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 

 vibratile 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 vibratile lobes. These few facts 

 tend to show that this larva will agree with the Tr. esculentus-l&rYa also 

 in the later stage, and also that it takes an equally long time 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 larvse. Partly the shape 

 of these larvae 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 Tr. esculentus-larvse, 

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

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

 stage, where it cannot be distinctly observed. 



Lytechinus variegatus (Lamk). 



PI. Ill, Figs. 1—2; PI. VIII, Fig. 1. 



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

 nenfi) (under the name of Toxopneustes variegatus) 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 Moira atropos some few specimens "of a purely maternal 

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

 paper on Echinoderm Hybridization outline figures are given of these 

 larvse. 



The fertihzation and the first embryonal stages of this species were 

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

 the Pluteus-shape. 



^) D. H. Tennent. Variation in Echinoid Plutei; a Study of Variation under Laboratory 

 conditions. Journ. Exper. Zoology. 9. 1910. 



D. H. Tennent. Echinoderm Hybridization. Publ. No. 132 of the Carnegie Institution. 

 1910. • 



2) E. Selenka. Beobachtungen iiber die Befruchtung und Theilung des Eies von Toxo- 

 pneustes variegatus. Erlangen 1877. 



E. Selenlia. Keimblatter u. Organanlage d. Echiniden. Z. wiss. Zool. 33. 1880. 



E. Selenka. Befruchtung des Eies von Toxopneustes variegatus. Ein Beitrag zur 

 Lehre von der Befruchtung und Eifurchung. Zoologische Studien. I. Taf. I — III. 1878. 



5* 



