58 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



the mesoderm of the mesentery, and consist of a fibrous membrane 

 lined by a layer of endodermic cells ; they contain one or more layers 

 of round or somewhat angular cells ; the spermatozoa appear as a 

 granular mass, and develop at the expense of the lining cells. There 

 is no permanent duct, but a temporary invagination, followed by 

 rupture, of the fibrous coat takes place at one point. The mesenteric 

 cavity is often occupied by some numbers of a species of Infusorian, 

 provided with a series of oblique, raised, ciliated bands. 



Bunodes verrucosus (B. gemmacea of Gosse) : Tentacles. — A 

 granular supra-mesodermal band contains some cells regarded as 

 vibratile, and provided with basal nucleated processes formed by the 

 cell-wall, connecting them with the mesoderm. This tissue consists 

 of longitudinal bands exactly resembling the connective tissue of higher 

 animals. 



Body-u-aUs. — The small warts of the column consist entirely of 

 ectoderm, and like the oval hyaline spaces of the surface their elements 

 are glandular cells, of which two types may be distinguished : the one 

 club-shaped, strongly granular, not nucleated ; the other, less abundant, 

 is saccular, with an opening to the surface, with hyaline contents 

 and nucleus. The glandular warts thus constituted originate in folds 

 of the ectoderm as conical elevations of that tissue, which sink into 

 the mesoderm, lose their ciliated cells, and become more or less shut 

 off from the ectoderm, which closes round their sides ; their function 

 is to secrete mucus. The rest of the ectoderm consists of elongated, 

 ciliated cells, in addition to the glandular ones found in the warts. The 

 mesoderm is made up of an external, bilaminate, fibrous, and an internal 

 muscular layer ; the external layer consists of loose connective tissue, 

 the inner one of wavy laminte, indented by circular folds. The 

 endoderm-cells are delicate, and contain fatty globules. 



Mesenteries. — They may be studied with unusual ease in this species 

 by sections. They present a number of deep folds on one of their 

 sides. The foot-disk has a special contractile layer, consisting of 

 radiating fibres ; these, with the ordinary circular muscles and fibrous 

 tissue which is connected with that of the mesenteries, constitute the 

 apparatus which fixes the animals. 



Corynaciis viridis : Tentacles. — The terminal knob is due to the 

 superior thickness at this point of the ectoderm, which in the tentacles 

 is mainly composed of thread-cells, with a few cnidocil elements. 

 Body-ivalls almost entirely made up of glandular cells ; a few elon- 

 gated cells, perhaps ciliated, also occur, and some thread-cells in which 

 the filament is irregularly rolled up, and which are the largest found 

 in the Actiniaria. 



Sagartia Penoti. — The male organs resemble those oi Actinia mesem- 

 hryanthemum in the relations of the testes and their method of dis- 

 charge. The observations of Heider on the genus are confirmed as to 

 all other points. 



Calliactis effoeta (Sagartia parasitica Gosse) : Tentacles. — The 

 epithelial elements of the ectoderm are remarkably varied, and include 

 club-shaped forms, forms \dth a basal fibril, and others, j)robably 

 sensory, which are constricted above the nucleus, and thence produced 



