121 



Meoma grandis Gray. 



Younger specimens of this species were fairly common in quite shallow 

 water along the sandy shore of Taboguilla in the Gulf of Panama, while 

 larger specimens were found only in somewhat deeper water, ca. 8 — 10 

 meters; especially at the little island of Tortola they occurred in great 

 numbers. Fertilization was undertaken on the 21st of December 1915. The 

 cleavage had the appearance of being somewhat unusual, the cells not 

 separating completely; but this could not be ascertained beyond doubt, 

 the fertilization being made in the evening. The gastrula-stage was reached 

 at the age of 14 hours; the embryos had an unusually thick ectoderm and 

 small cleavage cavity. Already at the age of 20 hours they had assumed 

 the shape of small Plutei, with distinct postoral arms. The posterior pro- 

 cess did not appear until the 3rd day. I did not succeed in rearing the 

 larvae beyond the first stage. 



The shape of the young larva is that typical of Spatangoid larvae. There 

 is a large patch of red pigment in the end of the postoral arms and of 

 the posterior process. In the skeleton (Fig. 52) the broad ventral trans- 

 verse rods are noticeable. The postoral rods are fenestrated, excepting 

 the lower part; also the lower part of the posterior rod is unfenestrated. 



Echinocardium australe Gray. 



Fertilization of this species was undertaken on December 28th 1914 

 onboard the "Hinemoa" off the northern coast of New Zealand. The larvae 

 developed normally until the formation of the posterodorsal arms, but 

 not beyond that stage. Further material was, however, obtained from 

 some plankton samples from Welhngton Harbour. No other Spatangoids 

 occurring there ( — a species of Brissopsis was obtained farther North, 

 off Bare Island, but this could hardly come into consideration on this 

 occasion — ), it is beyond doubt that these larvae belong to Echinocardium 

 australe. 



Although none of the larvae are in a very good state of preservation, 

 it is evident enough that they agree very closely with those of Echino- 

 cardium cordatum, as might be expected on account of the fact that it is 

 hardly possible to distinguish the adult specimens of these two "species". 

 I have the impression that the larva of Ech. australe is somewhat smaller 

 than that of Ech. cordatum, but it will be necessary to study the living 

 larvae of E. australe in order to ascertain whether a specific difference 

 between the two forms can really be pointed out. 1 have made no notices 

 about the coloration of the Ech. australe-larwa.. 



16 



