43 



a basket structure; the postoral rod is feneslrated. The skeleton is only 

 very slightly thorny. 



Beyond this stage I did not succeed in rearing I he lame. No figures 

 ean be given, because the "laboratory" conditions al Ililo did not permit 

 any drawing of the living larva 1 , and the skeleton has been dissolved 

 in the preserved specimens. 



The very conspicuous difference in the skeletal structure between the 

 larva? of this species on one hand (basket-structure and I'enestrated rods) 

 and the other Lytechinus-species on the other hand (no basket-structure, 

 no fenestrated rods) would seem to necessitate the conclusion that 

 the species vcrruculalus cannot be congeneric with the other 

 Ly/ec/un us-species, but should form a separate genus, in spite of tin- 

 fact that it seems lo art'ord no very prominent structural di {Terences 

 from those species. 



Toxopneustes pileolus (Laink.) 



I'l. VIII Fig. 8. 



Fertilization of this species was undertaken repeatedly during the 

 months April, May and June 1!H I at the Biological Station al Misaki. 

 In no case did I succeed in rearing the larva beyond the 

 first larval stage; evidently it is not very hardy, since 

 other Echinoid larva 1 (e. g. Ilcliuciilaris luberculala) were 

 reared to their full shape under quite similar conditions. 



The gaslrula stage was reached at about 2-1 hours 

 age, and al Ihe age of about two flays the skeleton 

 had begun lo appear and also the first indication of 

 the postoral arms was evident. The shape of Ihe young 

 larva (PI. VIII Fig. 8) is the usual, with a short, trunc- 

 ated body. One of the cultures was kept for about 3 

 weeks, but even at thai age the larva 1 had not yet 

 developed beyond the first stage, I lie only clilTerence 

 from the younger specimens being that the posloral 

 lobe had become distinctly concave in the middle at 

 the oral edge an indication that vibratile lobes will 

 be found in this larva. The pigmentation is not very 

 prominent; there are some scattered, red pigment cells 

 and Ihe points of the arms are reddish. The skeleton 

 forms a basket structure (PI. VIII Fig. 8; Fig. 1(1): both 

 the body rod and the recurrent rod are somewhat 

 thorny. There is a deep sinualion al the point where 

 the body rod and the postoral rod join; the latter is Letters as in fig. 5. 



6* 



[.-j,,. 1M . skeleton oi 

 llu ' y<>""K 'ana <>i 



