8 VERRILL 



Perhaps the sudden appearance of great numbers of young star- 

 fishes on certain oyster grounds, where they were not found pre- 

 viously, may be accounted for in this way. When well fed on young 

 oysters, these little baby starfishes grow rapidly and soon become 

 large enough to attract attention and do great mischief, even in one 

 season. 1 



Certain genera and species of shallow-water starfishes, and per- 

 haps a large proportion of the deep-sea species, do not produce so 

 many minute eggs, nor do these develop into free-swimming larvae. 

 On the contrary, the mother retains the eggs and cares for them till 

 they pass through an abbreviated metamorphosis and develop into 

 minute young starfishes provided with " sucker-feet " or podia to 

 enable them to take care of themselves. 



Commonly, in such cases, the eggs and young are held under and 

 around the mouth in large clusters. During the time required for 

 their development the mother appears to be incapable of taking any 

 food, owing to the obstruction of the oral region. The young are 

 often attached by a larval actinal pedicel in clusters or strings. 



This is the mode of carrying the eggs and young observed in sev- 

 eral species of Henricia, Anasterias, Sporasterias, and Podasterias, 

 and in numerous small species of Asteriidae, belonging to the genus 

 Leptasterias. I have personally observed this in L. compta, L. tenera, 

 and L. tittoralis of the New England coast, and in L. epichlora and 

 cribraria of Alaska. The young of epichlora were collected by Dr. 

 W. R. Coe. (See pi. LXXXV, figs. 2, a-/.) In all these the genital 

 pores are on the ventral side, near the mouth. 



In some other cases (Leptychaster) the mother carries the eggs on 

 the back, between the spines. 



Another method occurs in the genus Pteraster, and probably in all 

 the related genera of the family Pterasteridae. In these there is 

 a large dorsal " nidamental pouch," marsupium, or better, gono- 

 codium, for the retention of the eggs and the development of the 

 young, which remain in it until fully formed and sometimes up to 

 10 to 15 mm. or more in diameter. 



This gonocodium is formed by a tent-like membrane, which is 

 supported and kept stretched by the tips of slender, elongated, 

 radiating spinules, arising from the dorsal ossicles, and long enough 



1 Starfishes that have such minute eggs and young usually have minute 

 genital pores, situated in pairs, dorsally, in the interradial areas. Those 

 that have large eggs that they carry around or over the mouth have the 

 genital pores larger, on the ventral side near the mouth, so far as observed. 



