95 



the suggestion that also embryonic ophicephalous pedicellariae might be 

 found in Cidarids. 



The possibihty that Echinopluteus transversus may belong to Cidarids 

 is thus not entirely excluded. But at present the interesting problem of 

 the parentage of this remarkable larva is insolvable. 



Clypeaster japonicus Doderlein. 

 PL XIV, Figs. 2—3. 

 Th. Mortensen. On the development of some Japanese Echinoderms, p. 547. 



Fertilization of this species was undertaken at Misaki on May 24th 

 and again on June 18th, the embryos in both cultures developing until 

 the beginning formation of the posterodorsal arms, but no further. The 

 full larval shape was accordingly not reached, but still the larvae were 

 sufficiently advanced to show that they are in the main like those of 

 the other Clypeastroids thus far known. 



The eggs are extraordinarily clear and must be especially good objects for 

 cytological studies. They appear to be normally surrounded by a wide, quite 

 transparent mucilaginous coat, which may, however, easily break, when 

 the eggs are taken from the ovary, so that both entirely naked eggs 

 and such as are surrounded by the mucilaginous coat are found among 

 one another. Both are fertilized, though not quite so fast in the case of 

 those with the coat. — The cleavage does not present any specially note- 

 worthy features. Swimming gastrulse were found after ca. 14 hours. They 

 are oblong, showing a great number of mesenchyme cells wandering into 

 the blastocoel cavity from the oral pole, where a very active multiplica- 

 tion of the cells must take place. In embryos a little more than two 

 days old the formation of the skeleton is beginning; they are still in the 

 gastrula stage, the larval mouth having not yet been formed; the 

 archenteron is very narrow, and upon the whole the shape is rather 

 characteristic, as seen in PI. XIV, Fig. 2. Some red pigment has appeared in 

 the point of the beginning postoral arms. Four days old embryos have 

 assumed the typical Pluteus shape. In larvae eleven days old the postero- 

 dorsal arms had begun to appear; beyond this stage they did not develop. 



The shape of the larva (PI. XIV, Fig. 3) appears to be that typical of 

 Clypeastroid larvae, so far as can be judged from the stage of develop- 

 ment reached. The body is short, the oral lobe fairly high. The arms are 

 broad and flat, of the same width in their whole length. The postoral 

 band is slightly concave in the middle, making a deep curve on each side 

 before passing on to the postoral arms. A distinct hne is seen passing 

 from the lower point of these curves across the esophagus, indicating the 



