1. 秋に現れるスナヤツメLampetra planeri (Bloch)は兩背鰭が分離し二次性徴を缺く。
2. 此の状態は翌春産卵期の約1ケ月位前まで績く。その後次第に兩背鰭は連績し二次性徴も現れ,始めて,遂に産卵期にはtypicalなスナヤツメに變化する。
3. 産卵期のスナヤツメの齒は秋期のものより多少退化の傾向がある。
4. 産卵期のスナヤツメは秋期に於けるものよりも2～3cmの體長の縮小を行つてゐる。
5. カハヤツメの一異型Lampetra fluviatilis minor Kudo et Asada は恐らくスナヤツメの産卵期以前のものであらう。
6. ミツクリヤツメLampetra mitsukurii Hatta もスナヤツメと同樣産卵期以前に於ては,兩背鰭が分離し二次性微を缺く。此状態のものはカハヤツメ L.fluviatilis (Linué)に甚だ酷似してゐる。恐らく兩者は同一種のものであらう。

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Von den Planktoncyanophyceen in japanischen Binnengewässern wurden pier noch weiter folgende drei beschrieben :
Coelosphaerium Naegelianum Ung. (Taf. I, Fig. 1-3)
Fundort : Ryoshi-ko, Hokkaido.
Anabaena.flos-aquae (Lyngb.) Breb. var. Treleasi Born. et Flah.
(Taf. II, Fig. 6-9)
Ftmdort : Akan-ko, Hokkaido.
Anabaena Scheremetievi Elenkin var. recta Elenkin f.rotunclospora Elenkin
(Taf. I, Fig. 4-5)
Fundort : Ein Brackwasser-Teich in Chiba Provinz, Honshu.

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There is a small bog lake by the fishery village of Tokotan situated 4 km from the Akkeshi Marine Biological Station on the coast of Akkeshi Bay. The lake is elongated elliptical, 150 m in .length, 47m in greatest width, and 3.5m in greatest depth. It is surrounded by Sphagnvm-moss and is connected by a short canal with Lake Tokotan which is larger than the former and not boggy. Floating lakeward margins are 2-6m in width and mainly consist of a network of stems of Menganthes trifoliata growing thick around the lake. Colour of water is deep brown. The transparency varies from 1.15 to 1.70 in meter and is changeable dependent upon the amount of zooplankton, especially Rotatoria which are the most important group in the plankton of this bog lake. Bottom deposits are generally composed of peat debris. Thermal stratification was observed during June-September in summer and during December-March in winter, and the spring overturn is frozen through the winter stagnation period. takes place in April and May and the autumn one in October and November. The surface of the lake The water of this lake is generally acid (smallest pH value, 6.05), but surface water is sometimes weakly alkaline (greatest pH value, 7.4). Dissolved oxygen is often free in a thin layer of deeper water immediately above the bottom during the summer stagnation period.
From this hog lake and also from Lake Tokotan, have been known seven kinds of fishes, including Cyprinus carpio L., Carassius auratus (L.), and Hypomesus olid a (PALLAS), etc. as usefull fishes. Some of C. a'uratus are of reddish colour in natural propagation. Such naturally reddish coloured individuals inhabiting lakes are distributed on the Pacific coast of the eastern part of Hokkaido. There have been found in this lake 2 species of Mollusks, 2 of leeches, 1 of lsopoda, and several kinds of insect larvae from Merzyantlaes zone, and also found 2 species of Mollusks and one fresh water sponge from the next Equisehon-zone of 1-2 m wide.
Zooplankton is considerably superior to phytoplankton in amount. The decrease of the latter seems to be mainly due to the fact that the latter becomes prey of the former. The following pelagic animals were detected in the plankton of this lake: 2 kinds of insect larvae, 1 Hydracarina, a single form of Copepoda, 3 Cladocera, 1 Nematoda, 21 species of Rotatoria, 1 Gastrotricha, 18 Ciliata, 8 Amoebina including some of Testacea, and 2 Heliozoa. Insect larvae belonging to bottom dwellers are common in deeper water, but Copepoda and Cladocera occur more frequently in surface collections of summer plankton. The Rotatoria are the most abundant among the zooplankton and richer in the surface layer than in the deeper one.
The Ciliata are very rare in surface water, being abundant near the bottom where the amount of dissolved oxygen is scarce or free. The Amoebina are not found in surface collections, but found very rarely in deeper water only in summer. The Flagellata are the most excellent quantitatively in the phytoplankton of this lake, 21 species being secured, 23 forms of Chloropbyceae, 22 species of Facillarieae, and 5 kinds of Myxophyceae, have been found. Most of these usually appear very rarely in deeper water of the lake.
The small boa lake at Tokotan is of the distrophic type, but is not poor in production of zooplankton as compared with eutrophic lakes in Hokkaido.

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1. スデヱビは湖岸至る所に廣く分布し.底質及び水生植物の繁茂の有無と分布との關係は顯著でない。
2. 夏期に於ける深度と分布との關係に就いては,水深25m迄は比較的多數棲息し,特に15m以淺は最多數を示し,30m以深は激減す。本湖の水温躍暦は10～15mである點から,蝦は水温.10℃以上に好んで棲息するものの如くである。蝦の漁場は30m以淺である。
3. 雄蝦は雌蝦より軆小形で,雌蝦の生物學的最小鱧長は3.78cmを示し,體長4.5cm以上のものは殆ど全部雌蝦である。
4. 深度の相違に依つて性比を異にし,5m以淺に於ける雌蝦100尾に對する雄蝦の百分率は6%に過ぎないが,水深24～52mに於ては71.06%を占め,又,雌蝦の抱卵率は淺部94.3%,深部16.7%を示す。
5. 深慶の相違に依る體長の相違を認めたが,この原因ば性比に基くものである。
6. 抱卵數は體長と正比例して増加す。卵の大きさは1.3～1.6mmを示し卵徑は卵の發育に伴つて増加し抱卵數の多寡に關係しない。
7. 夏期蝦筌で漁獲される蝦の大きさは體長1.8～6.3cmで體長4.0～4.2cmが最多である。本蝦は1年で成熟するものの様で,産卵後も生き殘るらしい。

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1. 現歌に於てはFoxの發表しWhipple-Whippleの補正した飽和量表が最もよいと思はれる。
2. 0.1℃迄の値を内挿して表として掲げた。(第2表)
3. 水面所在高度の補正は必ず行ふこと。この補正表を掲げた。(第3表)

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