35 



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

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

 vibratile band was found to reach almost the |)osterior end on the sides 

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

 evidently the beginning of I he ventral vibratile lobes. These few facts 

 tend to show thai this larva will agree with the Tr. esculentus-\arva 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 larvae. I^artly the shape 

 of these larvae has been very perfectly preserved, because of the very 

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

 characteristic oblitpiely 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 Tr. esculenlus-hnvde, 

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

 and none of the latter larvae were preserved except a few of the oldest 

 stage, where it cannot be distinctly observed. 



Lytechinus variegatus (I.amk). 



l'\. Ill, Figs. 12; PI. VIII, Fig. 1. 



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

 nen t^) (under the name of Toxopneusies variegatus) partly as regards its 

 variations under laboratory conditions, partly in regard to hybridization, 

 for which pur])ose 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 Moira alropos some few specimens "of a purely maternal 

 form" were obtained; in PI. 2 figs. 18 — 20 and lextfigure 5, p. 138 of the 

 paper on Echinoderm Hybridization outline figures are given of these 

 larvae. 



The fertilization and the first embryonal stages of this species were 

 studied by Seleiika'-); he did not even rear them till they had assumed 

 the Pluteus-shape. 



') I). H. rciiiicnt. Variation in iM-liiiioiil I'lulci; a Sliidy of Variation iiiuU'r I,al)oratory 

 conditions. Journ. Kxpcr. Zoology. !•. litio. 



U. H. 'I'ennenl. I-k-liinodcrm Hybridization. I'uhl. No. 132 of the Cartiegic Institution. 

 1!)10. 



') K. Selenka. IJcohaclilungi'n iil)('r die Befriuiitung und Theilung di's Eies von Toxo- 

 pneusies variegatus. l-'rlangcn 1877. 



E. Selcnka. Kciniblatter u. Organanlage d. luliinidiMi. Z. wiss. Zool. .'53. 1880. 



E. Selcnka. Hefrui-litung des lues von Toxopneustes variegatus. Ein Beitrag zur 

 Lehre von der Bcfruchtung und ICifurchung. Zoologist-he Studien. 1. Taf. I — III. 1878. 



5* 



