12 C(el. 
CCELENTERATA. 
of the ovum and early stages in the development of Gorgonia verrucosa. 
The ovum is surrounded by a hyaline membrane, and is attached by a 
stalk to the mesentery. In the course of segmentation, there is a stage 
with sixteen segments, which is figured. The formation of the gastrula 
takes place apparently by dolainiuation. After the ciliated embryo has 
come to rest, an invagination of the unattached polo takes place, to form 
thq mouth and stomodaeum, but the communication between the oesopha- 
gus and body cavity is not effected until a comparatively late period. 
22. Lindstrom, G. Obersilurische Korallen von Tshan-tien. In Richt- 
hofen’s “ China,” iv. pp. 50-74, pis. v.-vii. 
23. Kowalevsky, A., & Marion, A. F. Sur le d^veloppement des 
Alcyonaires. C. R. cxv. pp. 562-5G5. Abstr. Ann. N. H. (5) x. 
p. 413, and J. R. Micr. Soc. (2) ii. p. 797. 
The authors describe their researches upon the development of two 
species of Clavularia and Sympodium coralloides. The fecundated ovum 
remains in C. crassa quiescent for some time before dividing. When seg- 
mentation occurs, it is, at first, very rapid. The primitive nucleus must, 
at its first division, be unable to carry with it the whole mass of vitellus 
as nutritive substanco. The derived nucloi undoubtedly emigrate to- 
wards the periphery, as is the case in some Crustacea ; but when they are 
numerous enough, they determine a splitting up of the vitellus, which 
becomes rapidly marked out, producing segmentation spheres, which 
penetrate angularly to the centre of the ovum. After this, the distinc- 
tion between a central nutritive part and a peripheral evolutive part per- 
sists in the segmentation spheres themselves. The larva, when it issues 
from the ovum, with its characteristic appearance, possesses at its two 
ends a certain number of nutritive globules floating in the liquid which 
occupies the whole cavity. The free-swimming existence of the laiva is 
short, and it soon fixes itself by its broader end, which is carried in front 
when swimming. The narrower end becomes gradually depressed, forms 
at first an ectodermic plate, in the middle of which there often rises a 
knob representing the extremity of the larva ; then it becomes invagi- 
nated, to form the oesophageal sac, the bottom of which has to become 
perforated to place the mesenteric cavity in communication with the 
exterior. In Clavularia petricola , we see as many as twenty-six primitive 
dissepiments at the bottom of the mesenteric cavity, their axes being 
formed by conjunctive streaks attached to the base of the ectoderm. It 
is only at the moment when the mouth is formed, that these dissepiments 
become regular ; eight of them grow rapidly, to join the oesophagus, while 
the others become gradually obliterated. 
24. Marion, A. F. The Alcuonaria of the Bay of Naples. Ann. N. H. 
(5) p. 406. 
25. . Les Alcyonaires du golfe de Marseille. C. R. xciv. p. 985. 
26. . Actinaires atlantiques des dragages de l’aviso ‘ le Travailleur.’ 
L. c. p. 458. 
