ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
489 
symbiosis. In regard to the revivification of Rotifers after desiccation, 
he denies the justice of the conclusions of Zacharias and criticizes 
some of Plate’s observations. He thinks it premature to conclude that 
only the moss-inhabiting Rotifers can survive desiccation, and protests 
against generalizing from a few observations. 
The author then describes the development of Callidina and Melicerta 
— the extrusion of the polar body, the segmentation, the appearance of 
the various organs, their subsequent differentiation, and the hatching. 
The ovum of Rotifers is bilaterally symmetrical ; the polar body is 
extruded on the dorsal surface of the future embryo, in Melicerta nearer 
the subsequent posterior pole, in Callidina almost at the subsequent 
anterior pole ; the first cleft separates unequal parts ; the smaller part, 
exclusively “animal,” occupies the lower end, the larger part, both 
“ animal ” and “ vegetative,” occupies the upper end. The segmentation 
is unequal, there is no segmentation cavity, the gastrulation is epi- 
bolic. There is no unified mesoderm comparable to that of worms 
and other bilateral animals. Only isolated organ-rudiments occur, of 
which only the granular cells outside the pharynx give rise to the 
elements of coelomic muscles. The skin muscles separate from the 
epidermis, the genital cells arise from the gut-rudiment, the cement- 
gland is an ectodermic invagination, the excretory system is at least not 
endodermic. The ectoderm is active in development, the endoderm 
is passive. 
In the occurrence of apical plate, longitudinal muscles, head-kidney, 
&c., the embryonic Rotifer is like a Trochophore, but there are no 
mesodermic bands. The Rotifer embryos are therefore below the 
Trochophore level. In the possession of a post-oral ventral ganglion 
they approach the Trochophore of Molluscs, and they show affinities 
with the type from which Nematodes, Polyzoa, Brachiopods, and 
Chaetognatha are derivable. In the possession of a post-abdominal 
region during development and in the occurrence of mobile appendages 
in Hexarthra they approach Crustacea. Finally the development 
suggests derivation from the Protrochophore of Plathelminthes. 
Echinodermata. 
Origin of Radiate Symmetry.* — Prof. 0. Biitschli makes a strenuous 
attempt to show how the radiate symmetry of Echinoderms may have 
arisen from a bilateral condition. His general idea is that the ancestral 
form fixed itself on its right side, and that there ensued a partial reduc- 
tion of that side. It is not possible, however, to follow Biitschli’s 
intricate speculation without constant reference to his figures. 
Echinoderms of Kingston Harbour, Jamaica. +— Mr. G. W. Field 
reports that the Echinoderm-fauna of Kingston Harbour is rich be- 
yond expression, especially in the numbers of individuals of many of the 
species, twenty-eight of which were noted. The most abundant is 
Toxopneustes variegatus , which is found over almost the entire bottom of 
the harbour ; its eggs are the most favourable for study the author 
has ever seen, and the larvae can be easily reared. It is able to hide 
* Zeitsckr. f. Wiss. Zool., liii. Suppl. (1892) pp. 136-60 (1 pi., 4 figs.), 
t John Hopkins Univ. Circ., xi. (1892) pp. 83-4. 
