of the Fishery Board for Scotland. 



231 



At 1 p.m. one of the eggs showed a number of little protoplasmic pro- 

 cesses sticking out at right angles from the zona (fig. 8). They seem to 

 be detached from the zona, though probably connected by a very fine pro 

 toplasmic thread, which was invisible under Zeiss 1)D. The sperms 

 kept boring away, but did not seem able to get closer to the zona than s 

 shown in fig. 8. There was a protoplasmic boss sticking out of the 

 micropyle. This was generally present, and usually on the lower side of 

 the egg. 



One egg had its zona covered with papillai. Another had three or 

 four sperms stuck with their pointed euds against the zona. A clear 

 layer outside the zona was made out in one egg; it seemed to me merely 

 an exudation of protoplasm. 



The inner of the two zona layers is applied close to the yolk, 

 as is shown by the protoplasmic boss, which is constricted by it 

 (fig. 18). A narrow clear division is seen between the two layers of 

 the zona. 



At 3 p.m. segmentation had occurred in several eggs. In one egg the 

 division into two was proceeding from one side (fig. 10). Another egg was 

 segmented into a macromere and a micromere ; the protoplasmic boss was 

 on the macromere (fig. 21). Sometimes it stands right across the 

 dividing line. Figs. 10, 11, 13, 20, 21, 22, 28, and 29 represent 

 conditions found at 3 p.m. Most of the eggs were in the two-celled 

 stage (fig. 13). 



Some eggs had taken a kidney-shape, having a hilum deeply inserted 

 (fig. 20). The niche was filled up partly with translucent material. The 

 zona seems to thin away over the notch sometimes. The division of the 

 egg takes place within the zona, and is not apparently taken part 

 in by the zona. 



In the two celled stage, one egg after being quashed retained its 

 previous two-ceiled shape (fig. 38). A nucleus was seen in it ; it simply 

 showed a little sphere with yolk granules attached. Round the inside of 

 the investment there was a number of small clear corpuscles larger than 

 yolk granules. The yolk granules when poured out oscillated. 



In one case of crushing the egg I saw some clear protoplasm of yolk 

 granules after they issued form into a sphere exactly resembling a 

 nucleus. The yolk corpuscles caused the "nucleus" to quiver. Then the 

 excess of yolk granules moved away from it. 



The nucleus seems to mean simply a collection of clear protoplasm in the 

 centre of the cell. It may, on the egg being crushed, break up, or it may 

 retain its shape after the yolk granules have poured out. In the 

 developing egg the nucleus is not intimately bound to the yolk granules; 

 in the ripe egg it is distributed through the egg mass. 



In a three-celled stage a little clearer area in the centre indicated the 

 presence of a nucleus in each cell (fig. 1 7). When the eggs were crushed 

 the nuclei were seen to be similar to the nucleus of the ripening egg — a 

 clear vesicle-like body showing no structure under Zeiss D.D. and 

 oc. 2 (fig. 14). The nuclei were visible externally first in the three-celled 

 stage. 



Division into four cells was noticed (fig. 30). 



At 7 p.m. development had not proceeded further than at 3 p.m. 

 Fig. 25 represents one of the eggs at that time. 



By the next forenoon, the eggs in the dish had not advanced; they ap- 

 peared to be dead. A number of them had a gelatinous network round 

 them. One egg which showed a gelatinous outer network measured 

 •06mm. in diameter ; it is small, and may have lost some of its contents. 



On June 5 a new lot of eggs had been spawned 



