194 CARNEGIE INSTITUTION OF WASHINGTON. 



Of Diadema ouly the first larval stage was reached, the culture being 

 accidently destroyed when a week old. All efforts to get a new culture 

 started were in vain, the breeding-season of this species being then passed, 

 although only a week before several specimens were still found containing 

 ripe sexual products. Tripneustes esculentus and Lytechinus variegatus were 

 raised until the beginning of metamorphosis, Echinometra lucunter and 

 Mellita G-perforaki through the complete metamorphosis. The Mellita larva 

 shows the structure typical of clypeastroid larva ; the other larvse all belong 

 to the type with a posterior cross-rod in the final larval stage, the body 

 skeleton in the first larval stage forming a frame. Lytechinus is, however, 

 })eculiar in that no frame is found in the first larval stage. 



No other echinoids were found ripe during the time the expedition stayed 

 at Tobago. Of asteroids, only one species, Ophidiaster guildingii, was found 

 ripe, and that not until the very end of our stay, so that the fertilization 

 could not be undertaken until 3 days before we left. Accordingly, only the 

 very youngest larval stage was reached, but, nothing being known hitherto 

 regarding the development of any of the Linckiidse, the fact here discovered 

 that this species has a typical bipinnaria larva is of interest. 



For the ophiuroids, the season was rather too early, most of the species 

 being unripe. Of 3 genera, however, the development could be studied, 

 namely, Ophiothrix, Ophionereis, and Aniphiura. The Ophiothrix larva closely 

 resembles that of Ophiothrix fragilis, the skeleton being of the same type as 

 in that larva. The Ophionereis larva, although free-swimming, does not 

 assume the shape of a pluteus. It is worm-shaped, without any trace of a 

 larval skeleton; the metamorphosis is completed in about 3 days. The 

 Amphiura was found to be viviparous. 



While the holothurians did not yield any results, the single crinoid occur- 

 ring at Tobago, Tropiometra carinata proved to be a very favorable object 

 for embryological study and its development is of more than usual interest. 

 The eggs are not held on the pinnules, but dropped free into the water. 

 The fertihzation membrane is finely sculptured, closely set with small spines. 

 The embryo, which has the same shape as the Antedon larva, swims very 

 actively for a period of about 3 days, when it attaches itself; but if no suit- 

 able place of attachment is found, it may continue its free-swimming Hfe, 

 and in some cases it was found not to attach itself until it was 8 days old. 

 The pentacrinoid and its growth-stages have not been studied in detail; 

 reference must be made to the final report on the development of this crinoid, 

 which will appear later. The full report on the other echinoderms studied 

 during the expedition will be incorporated in the report on the studies on 

 echinoderm development carried out during the winter's voyage in the 

 Pacific regions in 1914-15. 



Studies on Alcyonaria, by L. R. Cary. 



The examination of specimens of several species of Alcyonaria growing on 

 tiles, all of which were in relatively shallow water, showed that in many 

 instances the growth had been only about 5 per cent annually for each of 

 the past three years. The average size of specimens of the same species 

 occurring on the reefs in depths of from 1 to 18 meters must necessitate 

 either a very long period of growth, or else the gro^vth must have been much 

 more rapid than that shown by the specimens on the tiles. These facts 

 were brought to my attention last season, when the deeper reefs were studied 

 by the aid of diving apparatus. At that time an equal number of tiles with 

 specimens of the same species of gorgonians were placed on a reef in water 



