43 



a basket slruclurc-: llio posloral rod is fenestrated. The skeleton is only 

 very slighlly liiorny. 



Reyond this slai^e 1 did not sncceed in rearing the larva*. No figures 

 can be given, because the 'laboralory" conditions at llilo did nol |KMinit 

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

 in the preserved specimens. 



The very conspicuous iliU'erence in the skeletal structure between the 

 larvae of this species on one hand (basket-structure and fenestrated rods) 

 and the other L/y/cr/j/nf/.s-species on the other hand (no basket-structure, 

 no fenestrated lods) would seem to necessitate the conclusion that 

 the species verruciilaliis cannot be congeneric with the other 

 Ly{echinus-!>pc clcs, but should form a se])arate genus, in spite of the 

 fact that it seems to ad'ord no very prominent slruclural dilTerences 

 from those species. 



Toxopneustes pileolus (Lamk.) 



PI. VIII Fig. 8. 



Fertilization of this species was undertaken repeatedly during the 

 months April, May and .lune 101 1 al llu' Biological Station at Misaki. 

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

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

 other Echinoitl larvae (e. g. Hcliocidaris luberculala) were 

 reared to their full shape under quite similar conditions. 



The gastrula stage was reached at about 21 hours 

 age, and at the age of about two days the skeleton 

 had begun to appear and also the first indication of 

 the postoral arms was evident. The shape of the young 

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

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

 weeks, but even al that age llu' larvae had not yet 

 developed beyond I he fust stage, the only difference 

 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 

 he foun<l in this larva. The pigmentation is not very 

 promineiil; Ihere are some scattered, red pigment cells 

 aiul the points of llu' arms are reddish. The skeleton 

 forms a basket slruclure (PI. VIII Fig. 8: Fig. 10); both pjg. lo. skeleton of 

 the body rod and the recurrent rod are somewhat Hi*-' young larva of 

 thorny. There is a deep sinuation at the point where feo/iw'sideview'^^/ 

 llie body rod and the postoral rod join; the latter is Letiers as in ng. 5. 



