ZOOLOGY AND BOTANY^ MICROSCOPY, ETC. 389 



one the name of A. triophthalma, because besides the frontal eye, 

 seated upon the oesophageal ganglion, it possesses two other smaller 

 eyes placed at a distance from the ganglion, and provided with visual 

 nerves. The male of A. Sieboldii possesses on each side of its body a 

 triangular process ; but no such appendages occur in the male of the 

 new species. 



Ecliinoderra.ata. 



Echinoderm Morphology. — Dr. P. Herbert Carpenter,* and W. 

 Percy Sladen,! have essays dealing respectively with the apical 

 system of the Ophiurids, and the homologies of the primary larval 

 j)lates in the test of brachiate Echinoderms. The latter sketches the 

 difference in the history of the development of the different groups, 

 after noting that during growth there is a more or less centrifugal 

 movement of plates, and that there are two natural sets of plates — a 

 basi-oral or interradial, and a radio-terminal or radial series. In the 

 earliest stages of the Crinoid the former primarily constitutes the 

 whole calyx ; during growth the radial series developes with dis- 

 proportionate rapidity, and at a comparatively early stage predominates 

 over the basal series. In the Ophiurid the radials are formed first, 

 and the basals appear later. In the Asterid, as in the Crinoid, there 

 is a retarded radial growth. In both A sterid and Ophiurid the outer 

 plate of the retarded series appears earlier than the inner, and in both 

 the representatives of the under-basals are not formed until the other 

 plates are well developed. Sladen thinks the facts now known point 

 to the conclusion that the Ophiurid is derived from a more highly 

 developed Crinoid than the Asterid, which arose from a more primitive 

 ancestor, and the two forms have advanced along collateral lines of 

 descent. In both Asterids and Ophiurids, plates — the terminals — are 

 found at the end of the arms, which are apparently without any 

 homologues in the Crinoid. Dr. Carpenter urges very strongly the 

 use of a reasonable terminology in the description of Crinoids. 

 Against the view that the under-basals represent the dorsocentral 

 plate of the young urchin, he puts forward the additional argument 

 that not only has Marswpites a dorsocentral plate as well as under- 

 basals, but the same is true of some Asterids and Ophiurids. 



Development of Comatula-J — E. Perrier recognizes three phases 

 in the life-history of Comatula — the Cystidean, Pentacrinoid, and free 

 Comatulid. 



At the end of the first phase the young has no buccal tentacles 

 or arms, its digestive tube forms a half-spire, and there is an anus at 

 the side of the body. A U-shaped tube serves to introduce vvater 

 into the tentacular apparatus, but it is not certain that it is the 

 homologue of the sand-canal of other Echinoderms. The stalk 

 contains six cords of cells, one of which is central, and is prolonged 

 into the swollen part of the body, so as to occupy the axis of the 



* Quart. Joum. Micr. Sci., xxiv. (1884) pp. 1-23 (1 pi.). 



t Tom. cit., pp. 24-42 (1 pi.). 



j Comptes Rendus, xcviii. (1884) pp. 444-6. 



