TROPIOMETRA CARINATA. 5 



deep sea, which have risen to the surface and there come under the influence 

 of currents. 



It is in accordance with the comparatively long period of active swimming 

 of the larvse that we do not find the Pentacrinoids attached to the cirri or 

 other places upon the adult. Indeed, I have not found any free Pentacrinoid. 

 Not knowing, then, whether the larvae prefer any special object upon which 

 to attach themselves, I tried different things — algae (especially Udothea and 

 Corallina), coral pebbles, bivalve shells, leaves of Zostera {Thalassia testudi- 

 num) — which I put into the jars with the larvae. Although specimens 

 attached themselves to almost all these objects, they did not prove equally 

 favorable. The most favorable attachments were made upon Udothea and 

 Corallina. A good many specimens attached themselves to the surface film 

 of the water, and here they developed into very fine Pentacrinoids. 



The greater number of the specimens which attached themselves to the 

 Thalassia leaves, dropped off and fell to the bottom of the jar, but continued 

 developing lying on the side, unattached. This had, however, a curious 

 effect on them : the vestibulary invagination did not close up and the thick- 

 ened skin of the bottom of the invagination continued to be in contact with 

 the anterior (by this time posterior) end, by which they ought to have been 

 attached. This thickened skin therefore acted as a band keeping the (now) 

 anterior end of the embryo down; the stem-joints keeping on growing 

 normally, the stem became more and more curved, the result being that the 

 embryo assumed a pecuHar shape, resembUng a pipe delate ix, figure 6). 

 Even in spite of this abnormal shape, some of these specimens went on grow- 

 ing and at last developed into Pentacrinoids differing from the normal ones 

 only by having the head bent downwards, and I can scarcely doubt that it 

 would have been possible to rear them to full development if time had per- 

 mitted. A similar aberrant development has been described by Barrois' in 

 his "Recherches sur le d^veloppement de la Comatule" (p. 640, plate xxx, 

 figure 21, etc.). 



On account of the short time of our stay at Tobago I did not succeed in 

 getting the Pentacrinoids very far in their development. On leaving the 

 island I carried some of my cultures along with me, in the hope that they 

 would stand transportation and go on developing. While staying in Port of 

 Spain, Trinidad, waiting for the steamer for New York, I had the cultures 

 placed in one of the laboratory buildings of the Botanical Garden, through 

 the kind permission of the director, Doctor Rorer. During these 5 days every- 

 thing went well, though there was no opportunity for changing the water. 

 On board the steamer it was difficult to find a suitable place for the cultures, 

 and one night, near New York, the temperature went down too far, so that 

 the Pentacrinoids were chilled. On my arrival at New York I had them 



' Reoueil Zoologique Suisse, iv, No. 4, 1888. 



