7. Anthozoa (incl. Hydrocorallia). A. Zoantharia. 25 



Faurot describes the development of Sagartia parasitica and Adamsia palliata. 

 At the close of segmentation a blastula, full of yolky substance, is produced, 

 which is, at first, irregular but later becomes spherical, ciliated, and pierced 

 with one or with several apertures. It then presents the appearance of a 

 planula but possesses ectoderm only. A typical invagination occurs (commencing 

 at an orifice on the surface) which becomes complete in spite of the yolk. As 

 soon as gastrulation is complete a contractile middle layer is formed and al- 

 most simultaneously the pharynx arises, not by invagination at the blastopore 

 but by a folding of the middle layer in the median region of the stomodseum. 

 The formation of the pharynx is therefore not the result of oral invagination 

 of a two-layered planula, nor of the introversion of the stomodseum of a gastrula. 

 At first the pharynx is a groove along one side of the body-wall and simul- 

 taneously with its formation the mesenteries 1,1 appear obliquely, being 

 formed either by the same or by an independent folding. The formation of 

 the mesenteries 2,2, 4,4, 3,3 may also be interpreted as due to oblique fold- 

 ing of the mesoderm of the body-wall. The pharynx becomes converted into 

 a tube only on the formation of these 3 pairs of mesenteries. The couple 3,3 

 appears rather lower down and somewhat later than the other 3 couples. The 

 author points out that the Hexactinise present during their development, in 

 regard to hypostome and mesenteries, characters which show affinities between 

 them and the Hydroids and AcalepLue. The group "Scyphozoaires" as described 

 by Goette and Delage & He"rouard ought to be suppressed. 



Annandalei 2 ) redescribes Hetridium scliillerianum and describes an isolated 

 race (var. exul) of this species from brackish ponds at Port Canning, Lower 

 Bengal. The variety has a much more elongate, almost vermiform, column 

 whose walls are thin, owing to the feeble development of the mesoderm. The 

 column of young specimens of the variety exhibits less divergence from that 

 of the typical form. The basal disc of the typical form is strongly muscular, 

 that of e. is less so but that of young examples of the latter resembles in its 

 general character, except in the absence of a sphincter, that of the typical 

 form. In young examples of e. the lower surface of the disc is flat (as in the 

 typical form) but in well grown individuals it is either concave or convex ac- 

 cording to external circumstances and is relatively small and degenerate, having 

 lost its function as an organ of adhesion in accordance with its change in habits 

 - for the new race, when full grown, lives buried in the mud, with only the 

 tentacles protruding, while the typical form is found attached to solid objects. 

 The movements of e. are more active than those of the typical form. The 

 colour of both forms is due to zooxanthellai, irregular solid particles and glo- 

 bules of liquid, and minute bodies of a deep violet colour (possibly algae). 

 There is a layer of water between the ectoderm and mesoderm of the typical 

 form, but not of the variety. There is one cycle less of tentacles and mesenteries 

 in e. than in the typical form and the adult of e. cannot withdraw its tentacles 

 into the body. The variety usually drags itself along by means of its tentacles, 

 a tentacle is stretched out to its greatest length, fixes itself by a mucous se- 

 cretion to some object and contracts, thus dragging the animal forwards. The 

 cells of the tentacle are drawn out into irregular projections at the points where 

 they are held hy the mucus. The author has observed the same phenomenon 

 in Hydra and suggests that this is an explanation of Zykoffs statement (1898) 

 that the ectoderm cells of this animal put out pseudopodia which are used in 

 progression. The evidence seems to indicate that the new race of schill. has 

 been evolved from the typical form, owing to a change of environment, since 

 the latter was described by Stolic/ka in 1868. 



