35 



The larvae were kept alive (in good condition) for 10 days, but did not 

 yet show any indication of the formation of the postero-dorsal arms. The 

 vihratile band was found to reach almost the posterior end on the sides 

 of the body, and the postoral band to form a little fold on each side 

 evidently the beginning of the ventral vibralile lobes. These I'ew facts 

 tend to show that this larva will agree with the 7V. f.sn//r///ii.v-hirva also 

 in the later stage, and also that it takes an equally long lime before 

 it develops into the full larval shape. 



Although the skeleton has been dissolved, it has seemed to me not 

 superfluous to give a pair of figures of the young larva-. Partly the shape 

 of these larva? has been very perfectly preserved, because of the very 

 slow dissolution of the skeleton (traces of it are still distinct), and the 

 characteristic obliquely truncate form of the body is thus well shown; 

 partly the figures show the suboral cavity to be very large and distinct. 

 The same will most probably be the case in the 7Y. esculentus-larvse, 

 but 1 have not observed it in making drawings from the living specimens, 

 and none of the latter larva- were preserved except a few of the oldest 

 stage, where it cannot be distinctly observed. 



Lytechinus variegatus (Lanik) 



PI. Ill, I'i.ys. 1 '2: PI. VIM. Kij-. 1. 



The larva of this species has been the object of careful studies by Ten- 

 nenl 1 ) (under the name of 7'oro/j//n/.s7r.s ixirici/alux) partly as regards its 

 variations under laboratory conditions, partly in regard to hybridization, 

 for which purpose it appears a specially favourable object. Nevertheless 

 a description of the larva has never been given: the later stages have 

 only been mentioned quite accidentally, through the fact that in a crossing 

 of this species with Aloira <tln>j)os some few specimens "of a purely maternal 

 form" were obtained; in PI. 2 figs. 18- 20 and I ex I figure 5, p. 138 of the 

 paper on Echinoderm Hybridization outline figures are given of these 

 larva?. 



The fertilization and the first embryonal stages of this species were 

 studied by Selenka 2 ); he did not even rear them till they had assumed 

 the Plu tens-shape. 



') I). II. Tcnni-nt. Variation in Echinoid Pluli-i: :i Study nl Variation nndrr Laboratory 

 conditions, .lourn. Exper. /.oology. !t. l!i|o. 



IX H. T iMi iii-n I. Ecliinoderin Hybridization. I'tibl. No. l.'i'J of tin- ('.arm-nil 1 Institution. 

 1910. 



2 ) E. Selenka. Beobachtungen ubi-r die Belruclitiin^ und Thc-ibmi; di-s Kk-s von Toxo- 

 pneustes varietal us. Krlangen 1.S77. 



E. Selenka. Keimblallcr u. ( >ri;un;mla^e d. Ei-hinidi-n. /.. \\iss. /ool. .'!.'!. IMXu. 



1C. Selenka. Hi-lruchtunn des Hies von Toxopnenslt-s varii-.yaluv Ein Ht-ilrat; zur 

 Lehre von der Befruchtun^ und Eifiirclumg. Xoologisdn- Slndien. I. Taf. I III. 1878. 



5* 



