110 



Dr. J, Beard. 



[May 16, 



When the egg is ripe, the germinal vesicle lies just nnder the shell 

 in a protoplasmic mass, which is permeated by very small yolk 

 particles. The sturgeon egg has a very similar structure, but the 

 yolk elements are much finer. The males are on the average only 

 half the size of the females, and are very much more numerous than 

 the latter, as others have noted. The spawning takes place between 

 May 20th and the middle of June. Some of the inhabitants of the 

 shores of Black Lake have seen it taking place in July. This appears 

 to me very likely. The fishes only spawn on warm windless days, and 

 if cold weather comes, they may remain away from the " points " for 

 weeks, as Garman already noted. 



I observed the spawning on three occasions, on May 24th, June 8th 

 and 9th. In the interval no eggs were laid, though search was made 

 for eggs and fishes every day by my assistants or myself. The 

 spawning takes place during the heat of the day, between 12 and 

 3 o'clock. A full account of it has been already given by Agassiz, 

 and quoted by Balfour and Parker. The eggs are thickly sown, and 

 cling to the small stones which lie about in the shallow water of the 

 " points." 



Certain spots seem to be traditional egg-laying grounds for Lepid- 

 osteus. The eggs are pretty easily removed from the stones, and my 

 own were hatched out in a Californian salmon hatching apparatus. 



Most of the eggs left on the stones fell a prey to fungi, and very 

 few indeed hatched out. With care and constant attention a much 

 greater percentage can be hatched out in the apparatus. The 

 difficulties of the investigation prevented the observation of the for- 

 mation of polar bodies. The segmentation is very rapid, and a cap of 

 small cells is formed in the course of five or six hours. The segmen- 

 tation is very unequal but in a sense complete. Eight furrows can be 

 traced to the centre of the lower pole. The attempt to segment the 

 lower hemisphere is, however, soon given up, none of the eight 

 furrows penetrate very deeply into the yolk, and none reach the 

 centre by a long way. They are only superficial furrows. 



The cell cap of the upper pole increases rapidly by divisions within 

 itself, and by the addition of fresh segments from the incomplete 

 segments below its margin. It grows over the yolk, and in the course 

 of 24 hours or less completely encloses the latter. A beautiful circular 

 blastopore is formed, from which a yolk-plug projects as in Amphibia. 



Before the close of the blastopore, the region of- the future embryo 

 is marked out by a blastodermic thickening, extending forwards from 

 the edge of the blastopore. 



A groove marking the axis of the embryo soon appears in this 

 thickening. It must be remarked that this groove appears only 

 just before the closure of the blastopore, and hence it cannot in 

 Lepidosteus be regarded as part of the latter. 



