Apparent non-Mendelian segregation encountered in a cross between adenine independent and adenine dependent haploid strains is explicable by postulating a multiple genetic control of adenine formation. One of these genes, which arose by spontaneous mutation in a originally pink adenine dependent culture, is presumed to block adenine synthesis prior to those already present in the stock. The postulated ad3 mutation is not linked with the other adenine genes, which, when mutant, cause color production, but it is epistatic to them.
1. The non-hibernating eggs of the silkworm were cauterized at the cleavage stages, 4 and 7 hours after egg-laying; they were fixed 84 hours after laying to examine the relational feature between the differentiation of germ cells and the degree of injury. 2. When the degree of injury falls within about 10% for the entire. circuit of the cross section of the egg, the non-splitted embryos are formed, while it is over 10% the formation of the splitted ones is resulted. 3. The germinal cytoplasm was found to exist in the silkworm; it corresponded to the presumptive genital region observed at the blastoderm stage. There was no correlational evidence between the extent of the germinal cytoplasm and the number of germ cells. From this result the proliferation of the primordial germ cells may probably go ahead the completion of the blastoderm.
Submicroscopic structure of the spermatid nucleus during its maturation has been determined by an electron microscopic examination of ultrathin sections. The constituent filaments making up the developing spermatid nucleus display a hexagonal array in a cross-section and a parallel array in a longitudinal section.
In this paper are described the results of the observations on the sex ratio and the chromosomes of Apus aecqualis (Fam. Apodidae) collected from a paddy field in the suburb of Numazu, Sizuoka-ken. Of 43 individuals collected, 34 were males, and 9 females. It has previously been reported that the males are rare in the member of this family, but the data at hand are incompatible with this general rule since there occur more males than females. It was found that the spermatogonial complement contained 12 chromosomes which consisted of a pair of large V-shaped elements and 5 pairs of small rod and V-shaped ones. The chromosomes are generally very small in size.
The nymphs of the grasshopper (Podisma sapporense) were exposed to radium in two groups for 1 and 3 hours. The various kinds of meiotic abnormalities were found to occur in the 1st and 2nd meiotic divisions of male germ-cells. They are as follows: coalescence and stickiness of chromosomes, formation of chromosome bridges, varying numbers of chromosomes, irregular arrangement of chromosomes in the metaphase plate and fragmentation of chromosomes. The type of abnormality closely resembles that caused by the treatment with high or low temperatures, and by exposure to supersonic waves.
In the present paper, it is reported that the Curled wing (Cw) and the chocolate (ch) are linked together with a crossing over value 11.10%. It seems probable to us that Cw, cf (crayfish) and normal genes are in a relation of multiple alleles, as the crossing over value between Cw and ch (11.10%) is pratically the same as that between cf and ch (11.32%), though a direct evidence for this conclusion is lacking so far, owing to the variable penetrance of Cw gene in heterozygotes Cw/cf.
With the purpose to explore the mechanism of the formation of lobated nuclei in the MTK-IV tumor, the daily frequencies in occurrence of tumor cells with lobated nuclei were experimentally studied in three clones derived from the original stock. The MTK-IV tumor is characterized by the occurrence of cells with lobated nuclei in 10 to 30 percent of frequency (Tonomura 1956). This study involves the following three experiments: (1) intraperitoneal inoculation with isolated nine tumor cells; (2) intraperitoneal inoculation with an isolated single tumor cell; and (3) intraperitoneal injection with the chemical (podophyllotoxin) after transplantation of the tumor. The single and nine-cell inoculations were made following the technique devised by Makino and Kano (1955) for the Hirosaki sarcoma. Podophyllotoxin used here is known as a powerful mitotic poison. The observations were carried out by means of the smear method with acetic dahlia. (1) Nine-cells clone (Fig. 3): A rat received nine isolated tumor cells developed a tumor in its peritoneal cavity. In the tumor samples taken on the 24th day after inoculation, the frequency in occurrence of tumor cells with lobated nuclei showed 76 percent. The tumor was transmitted by peritoneal injections for forty-three generations. The frequencies of cells with lobated nuclei increased during early transfer generations (Table 1-A). In the 43rd generation the daily frequencies of cells with lobated nuclei were 7 to 19 percent, being nearly identical with those of the original stock tumor. (2) Single-cell clone: In the ascites tumor which was developed through the introduction of a single tumor cell the daily frequencies in occurrence of tumor cells with lobated nuclei were observed. The frequency of tumor cells with lobated nuclei observed in the 1st generation is about 2 times higher than that of the original stock tumor. It gradually decreased towards the later generations. A percentage value identical with that of the original stock tumor was obtained in the observation of the 20th generation (Table 1-B). (3) Chemically treated clone: From the above results it is deduced that the formation of nuclear lobes in tumor cells is to be connected with an unfavorable environmental condition of the tumor. The following experiment was undertaken to ascertain the above assumption. Intraperitoneal injection With podophyllotoxin was made in tumor-bearing rats on the 2nd day after transplantation, and the change in frequency of tumor cells with lobated nuclei was studied (Fig. 6). The frequency observed prior to experiment was 12 percent. The highest percentage (32%) in frequency was obtained in the sample 12 hours after treatment. The tumor was transmitted for seven generations. In the 7th transplant generation, the daily frequencies of tumor cells with lobated nuclei were 9 to 13 percent, showing an approximately equal value to that of the original stock tumor. From the results obtained in the above experiments, the conclusion may be possible that the formation of nuclear lobes in tumor cells of the MTK-IV tumor seems to be closely associated with an unfavorable environmental condition of the tumor, or that nuclear lobes are to be formed when the tumor cells are exposed to an unsuitable condition.