IH SVEN LOVEN, ECHINOLOGICA. 



To tlie Echiiius miliaris Leske I am inclined to refer 

 the dennded specimen, Fl. F, fig. 29 — 38, whicli measures 

 2,5 mm. in diameter and is far advanced. Its spines were 

 strong, the gills apparently ready for their function. The 

 solitary interradials are all hut completely reabsorhed, only a 

 fragment of each remaining. The second peristomal ambiila- 

 crals are in part reabsorhed marginally; their ten persistent 

 j)rimordial plates, all poriferous, liave their circle removed 

 from the peristome, and the already broad interval is strewn 

 with Hakes of calcilied tissue, disposed in a certain order. 

 The branches of the auricles, fiy- 30, 81, the basal expansions 

 of which are marked off from the plate by a suture, are rising 

 and have begnn to diverge and to arch över the ambnlacra; 

 and, with all this, the aninial so near to having eompleted 

 its development, is still astomons. its mouth being overlaid 

 with the still persisting larval envelope, fig. 29, 32, more 

 strong and thick than in any of the young already described, 

 and protruding conically över the teeth which push from with- 

 in. The animal is aproetic also, fig. 34. The dorso-central 

 disk of the calycinal system is still entire, but has löst its 

 pentagonal ontline and nearly assnmed the rounded form of 

 the fnture anal membrane. It is thin and transparent, and 

 part of its substance is evidently reabsorhed. but there is as 

 yet no trace of its separation into ossicles or of an opening 

 between it and the eroded costals 1, 2 and 5. With this tran- 

 sitory condition and early evanescence the costals and radials 

 strongly eontrast. They are clothed with a rich epistrome, 

 (•lusters and rows of globules from under which spinary tu- 

 bercles are seen emerging, fig. 35 — 38. Here, as elsewhere, 

 the calyx is the stronghold of the epistrome. It is from this 

 and other particulars that I suppose this young animal to 

 belong to the Echinus miliaris Leske. 



These are details gathered from a few species of Ecto- 

 branchiates in early stages preceded by a prolonged free- 

 swimming pluteal existence. In essential points they agree 

 with corresponding stages of the young Cidarid. even when 

 this is derived from an exceptionally abridged marsupial 



' See the author"s Etudes s. 1. Echinoidées, p. ti7. and tlu; paper on the 

 .-species described by Linn.^us, p. 86, Pl. 7 — 9. In describing there the epi- 

 stroma, I overlooked the notes on it bv Al. Agassiz in Bulletin Mus. comp. 

 Zool. n:o 9. October 1869, p. 288. 



