216 SUMMARY OF CURRENT RESEARCHES RELATING TO 



That the Holothurians are not devourers of living corals is shown 

 not only in connection with the data just recorded, but from the fact 

 also that several of these animals were kept in a tank containing sea- 

 anemones and corals (Balanophyllia verrucosa) without their inter- 

 fering with them in any way, or manifesting alimentative functions 

 other than those just described. All that they require for their 

 nutrition is evidently derived from the coral or shell debris with 

 which they are customarily associated. At first sight this material 

 would appear to be in the last degree adapted for the sustenance of 

 such highly-organized animals, but, as may be confirmed at any time 

 by the investigation of like conditions in aquaria, it will be found 

 that shell-sand, gravel, and all other debris forming the superficial 

 layer at the bottom of the water, when exposed to the light, are more 

 or less completely invested with a thin pellicle of infusoria, diatoms, 

 and other microscopic animal and vegetable growths. It is upon 

 these minute organisms that the Holothurians feed, swallowing both 

 them and the shelly or other matter upon which they grow. 



Stalked Crinoids.* — P. H. Carpenter has a preliminary notice of 

 the stalked Crinoids of the Caribbean Sea, in which he has notes on 

 some old species, and on others either new or only briefly described 

 by Sir W. Thomson. Some observations on Holopus are mentioned, 

 and it is stated that the supposition that the tissues of this form are 

 very imj)erfectly difierentiated was found to be incorrect. The ovaries 

 closely resemble in structure those of Antedon eschrichti. 



New Deep-Sea Stalked Crinoid.f — Prof. E. Perrier describes 

 the fifteenth stalked Crinoid known to be now Hying— Dejnocrinus 

 parfaiti. This is distinguished by the calyx, which is formed of five 

 long hasals, separated by a circular groove from the five rudimen- 

 tary radials ; these are surmounted by five pre-axillary radials, 

 with which are connected five arms, which, as in Bhizocrinus and 

 Hyocrinus, are simple. Of all living fixed Crinoids, Democrinus has a 

 shorter transverse calycal axis, in relation to the diameter of the stalk, 

 than any other known form. This fact suggests that the stalk or 

 peduncle is an essential and important element in the determination 

 of the typical Echinoderm. In one example it was noted that the 

 stalk had two sets of roots, and thereby gave some indications of a 

 second stalk with a second calyx. If this view should be shown to be 

 correct, we should here have an example of a colonial or branched 

 Echinoderm. The author refers to the parallel he has drawn between 

 the Echinodermata and the Ccelenterata ; and reminds us that the 

 greater number of primitive Echinoderms were fixed ; although, as 

 might be expected, they are, like the Ccelenterata, radially symmetri- 

 cal, we have yet no example of arborescent forms. Democrinus 

 appears to diminish this distinction ; for, even if they did not live 

 in colonies, they show that the arborescent arrangement may obtain 

 in Echinoderms, as well as in Coelenterates. 



* Bull. Mus. Comp. Zool. Cambridge, x. (1882) pp. 165-81. 

 t Comptes Rcndus, xcvi. (1888) pp. 450-2. 



