Abstract
The chromosomes of the crayfish, Cambarus clarkii were investigated in spermatogenesis. This species was originally introduced from America. At present it abounds in the neighbourhood of Tokyo. The spermatogonial complex shows 192 chromosomes, of which 6 (3 pairs) are atelomitic V-shaped while the remaining are telomitic rod-shaped (Figs. 1-2). The haploid chromosome number, 96, was observed in the primary and secondary spermatocytes (Figs. 3-4 and 6). No evidence for the presence of the particular chromosomes could be found in the present species. The following table shows the numerical relationship of the chromosomes of the species belonging to the Potamobiidae so far studied.
