136 SUMMARY OF CURRENT RESEARCHES RELATING TO 



like those of Helix aspersa or other Pulmonates. In rare cases the 

 mitochondria of the typic spermatocytes are very large, coarse granules, 

 quite distinct from the smaller granules of the atypic series. The author 

 discusses the " Nebenkern " or " Golgi " apparatus. J. A. T. 



G-eiminal Nurse-cells of Testacella. — J. Bro>s^te Gatenby (Quart. 

 Journ. Micr. Sci., I'Jll), 63, 401—13, 2 pis., 21 figs.). In this slug 

 some of the germinal epithelial cells, instead of forming ova, spermatozoa, 

 and follicle-cells, become much enlarged to form yolk-cells or nurse- 

 cells, which have very large hyper-chromatic nuclei and a cytoplasm full 

 of yolk-discs. They nourish the ova and sperm-cells in spring and 

 summer ; they degenerate in part towards autumn and winter ; there is a 

 re-activation of some of them in the early spring, but degeneration again 

 occurs in many cases. The number of chromosomes in Testacella seems 

 to be something over twenty, and the haploid number over ten, probably 

 about twelve. The giant germ-cells seem to contain an irregular and 

 over-numerous series of chromatin loops. J. A. T. 



Gametogenesis and Early Development of Limnsea stagnalis. — 

 J. BEONTf: Gatenby {Quart. Journ. Micr. Sci., 1919, 63, 445-91, 

 2 pis., 6 figs.). In the oogenesis of this water-snail the germinal 

 epithelial cells show an excentric " Golgi apparatus " or " Nebenkern," 

 consisting of a number of rods (chondrioplasts or dictyosomes). In the 

 progerminative oocyte mitochrondria appear very early in the zone of 

 the Golgi apparatus. The Golgi rods divide by binary fission, and keep 

 increasing in number, each becoming provided with a small portion of 

 the included archoplasm. The apparatus spreads through the whole 

 ovum-cytoplasm. The mitochondria grow, divide, and spread uniformly. 

 The individual Golgi rodlet never grows beyond a certain size. The 

 first yolk-discs make their appearance after the Golgi elements and 

 mitochondria have spread far through the growing oocyte. Towards the 

 end of oogenesis the oocyte gradually becomes filled with fluid vacuoles. In 

 the spermatogenesis no mitochondria were discovered. In spermateleosis 

 (the metamorphosis of spermatid into spermatozoon) there is a mito- 

 chondrial residue sloughed off. The tail of the sperm appears as a new 

 formation of mitochondrial matter around the axial filament. The Golgi 

 apparatus is sloughed off during spermateleosis. The nuclear head is 

 very small compared with the long mitochondrial tail. In segmentation 

 the mitochondria are equally divided ; so is the Golgi apparatus ; both 

 persist in organogeny. J. A. T. 



Arthropoda. 



a. Insecta. 



Germ-band in Holly Tortrix Moth.— L. H. Huie {Proc. R. Sue, 

 Edinburgh, 1918, 38, 154-65, 2 pis.). The development of Eudemis 

 nsevana can be followed in the living egg with unusual clearness. 

 Beneath the inner pellicle is a finely and densely granular protoplasm, 

 and inside this is the yolk-plasm. Maturation takes place about the time 

 of oviposition ; the first polar body divides again. The first division of 

 ths zygote occurs two or three hours after oviposition ; in a few hours 



