lO DEAN. [Vol. XI. 



eersrs arc in fact sifted anions: the crevices of the rocks, and 

 are to be found many tiers below the uppermost layer. The 

 slime-covered character of the rocks seems little favorable to 

 the prolonged fixation of the eggs, and within two or three days 

 the majority become detached and are sifted deep among the 

 rocks. 



The color of the eggs at the time of extrusion is like that of 

 the sturgeon's, slaty gray, and is strong in color contrast to 

 the green-black rocks. About three hours later {early segmen- 

 tation) the eggs become creamy yellow ; two days later (end of 

 gastrulation) the color has changed to a dull shade of greenish 

 brown, although part of its duskiness may be due to the 

 sediment collected on the outer membrane. The lightness 

 in gravity of the animal-pole is early apparent, and when the 

 axis of the eggs is disturbed the germ-disk regains its upper- 

 most position in a surprisingly brief time, very much as in 

 Teleost or amphibian. 



As to the means adopted for securing embryological mate- 

 rial ; former experiments (Garman, Mark) had shown that 

 egg-bearing rock fragments taken on the spawning ground 

 might be retained in pans of water (renewed twice daily), and 

 the eggs successfully hatched. A more convenient method 

 was that of detaching the eggs from the stones while at the 

 spawning ground and hatching them subsequently in earthen- 

 ware dishes (Virchow^) or in a salmon hatcher (Beard). These 

 plans were found by the writer safe and convenient, none the 

 less because the natural hardiness of the eggs rendered them 

 little subject to attacks of fungus {Achlya): and by their use 

 there could certainly be no simpler way of securing develop- 

 mental stages, were it not that a single objection proves most 

 important : the eggs when collected are found to be of dif- 

 ferent ages, and in this confusion cannot well be reduced to a 

 complete series of stages. By use of artificial fertilization, on 

 the other hand, the writer found that every stage could be 

 secured conveniently and in suitable quantity. 



Artificial fertilization was first attempted at Lower Deep 

 Bay, the writer employing the same mode of procedure and 



^ According to Mr. Perry. 



