99 



between the stomach and the rectum, while the lower one lies on the 

 outside of the rectum. The postoral and posterodorsal rods are fenestrated; 

 they are slightly narrower in the basal part, the holes being there also 

 narrower and longer than in the outer part. Both are rather much thorny, 

 the posterodorsal rods are, however, nearly smooth along their inner side. 

 The anterolateral rods are distinctly thorny in their outer part; the dorsal 

 arch is very slender, smooth, often bent at an angle at the level of the 

 preoral band. 



Echinarachnius mirabilis (A. Ag.) 



PI. XIV, Fig. 4. 



Fertilization of this species, which occurs in quite shallow water, among 

 Zostera, near the Station at Misaki, was undertaken on June 1st 1914. 

 Unfortunately the culture was destroyed already the next day, and no 

 further opportunity was found for starting a new culture until towards 

 the end of the month, and then the breeding season of the species had 

 passed; at least, I did not find any specimens with ripe sexual products 

 by that time. Accordingly only very little information can be given about 

 the development of this species, and especially the characters of the larva 

 remain unknown. Still it may be worth while recording the few observa- 

 tions that were made. 



The eggs are surrounded by a mucilaginous coat with some red pig- 

 ment cells. This coat may be found floating empty in the water after the 

 embryo has been hatched, which does not happen till the embryo has 

 reached the gastrula stage, at the age of ca. 18 hours. The gastrula has 

 an unusual shape, like a pear (PI. XIV, Fig. 4); on leaving the egg-mem- 

 brane the pointed end is foremost. — The skeleton had not yet begun 

 to form, when the embryos died (probably because of the water being 

 very impure in those days). 



Echinarachnius (Dendraster) excentricus (Esch.) 



PI. XIV, Figs. 5—6. 



This species was found in great numbers in a locality near the Biological 

 Station, Nanaimo, viz. at Gabriola Island, in quite shallow water. While 

 some specimens were found buried in the sand, several inches deep, so 

 that no trace of them could be seen and they could be found only by 



one is a special formation, apparently of general occurrence among Clypeastroid-larvse. Thus 

 far it was unfortunate that in the "Echinodermenlarven d. Plankton-Expedition" (p. 74), 

 where the skeleton of the Echinocyamus-larva was used as an example, this lower rod was 

 designated as the "ventral transverse rod". — It should still be pointed out that this lower 

 ventral transverse rod does not correspond to the supplementary transverse rod of Echino- 

 pluteus transversus, which latter proceeds from the ventral recurrent rod. 



13* 



