CHAP. IV.] THE VOYAGE HOME. 211 



The process of propagation in Oj)hiocoma vivipara differs 

 from most of the other eases described, in the eggs being suc- 

 cessively hatched, and the young being found consequently in 

 a regularly graduated series of stages of growth. Although I 

 had not an opportunity of working the matter out with the 

 care and completeness I could have wished, I feel satisfied, 

 from the examination of several of the young at a very early 

 period, that in this case no provisional mouth and no pseudem- 

 bryonic appendages whatever are formed, and that the pri- 

 mary aperture of the gastrula remains as the common mouth 

 and excretory opening of the mature form. From the appear- 

 ance of the ovaries and of the broods of young, I should think 

 it probable that this species gives off young in a continuous 

 series for a considerable length of time, probably for some 

 months. 



I have selected these illustrations of the development of the 

 young of Echinoderms from the egg^ without the intervention 

 of a locomotive jDseudembryo from a much larger number. 

 As I have already said, I can not, on account of the unfavora- 

 ble conditions for carrying on such investigations under which 

 the majority of the species were j)rocured, say with certainty 

 that no trace of pseudembryonic appendages or provisional or- 

 gans exists in any of these instances, but I feel satisfied that 

 none such occurs in Psolus e])hipj)ifer, in Ilemiaster Philippii, 

 or in Ophiaeoma vivipara. Neither am I in a position to state 

 that in these southern latitudes direct development is univer- 

 sal in the subkingdom. I believe, indeed, that it is not so ; for 

 species of the genera Echinus, Strongylocentrotus, and AmMy- 

 pneustes run far south, and a marsupial arrangement seems im- 

 probable in any of these. It is, however, a significant fact that, 

 while in warm and temperate seas plutei and bipinnariae are 

 constantly taken in the surface-net, in the Southern Sea they are 

 almost entirely absent. 



Amidst all their general tameness the Falkland Islands boast 



