ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 57 



spaces between them. The endoclerm here is devoid of pigment- 

 corpuscles ; it is extremely delicate, for it often falls into a pulpy 

 condition during treatment. 



Body-walls. — The layers have the same general arrangement here. 

 In the ectoderm, however, thread-cells are very scarce, and the glands 

 are represented by clear spaces ; the layer appears to consist chiefly 

 of numerous fibrils set at right-angles to the surface, and dilated at 

 one or more points. The mesoderm and endoderm agree with those 

 of the disk. The mesenteries consist of strips of mesoderm, coated 

 on each surface by a longitudinal muscular layer, and this in turn by 

 endoderm. The reproductive organs originate in a kind of fold of the 

 mesoderm. The sexes are distinguished by differences of coloration. 



Actinia equina (A. mesembryanthemum of Gosse) : Tentacles. — Of the 

 three fundamental layers, the ectoderm has its outer surface thickly 

 set with cnidocils ; below these are numerous thread-cells. Body-ivalls. 

 — Their thickness varies with age ; thus, in a small adult, the ectodejm 

 and mesoderm together measure "085 mm. in diameter, in a larger 

 one • 6 mm. The ectoderm differs from that of the preceding species 

 in having ciliated cells much expanded at the free end, and a deep 

 fibrillated layer from which may be separated granular, nucleated, 

 " epithelio-muscular " cells, provided with a singly or doubly pointed 

 basal fibril, and resembling closely those of Hydra ; in the tentacles 

 they are much more distinct, club-shaped, and connected with the fibril, 

 which is here very short, by a peduncle. In some cases they have 

 one or two dilatations above the fibril. The writer will not adrnit the 

 distinctively nervous function of any of these cells, but regards them 

 as having joint epithelial and sensory functions, and as sometimes 

 giving origin to muscular fibres. The gland-cells of the layer have a 

 basilar process. The mesoderm and endoderm present the same 

 characters as in A. sulcata. 



Cliromatophorous Saccules. — Korotneff's chief results are confirmed. 

 Some elongated elements terminating in a kind of cup at the free 

 surface occur among the densely set external thread-cells ; the thick- 

 enings seen at various points of their lengths are really dilatations of 

 the cells, and not extrinsic to them. The usual granular band at the 

 base of the ectoderm is here wanting. In a few sections the mesoderm 

 exhibits nucleated cells. Though Korotneff found no connection 

 between the thread-cells and cnidocils, the former are now found to 

 originate each in a small protoplasmic mass at the external end of a 

 cnidocil cell, much as in Lucernaria. The ordinary ectodermal glan- 

 dular cells may have a basal hyaline process, but some elongated cells, 

 doubtfully granular, also occur here, ending on the surface by a 

 globular body, and bearing in their course dilatations, whose contents 

 are hyaline vesicles, not affected by colouring reagents, but re- 

 sembling adipose globules. The main function of the saccules is 

 probably sensory. 



CEsopJiagus and Mesenteries. — Not essentially different from those of 

 other Zoantharia. 



The Sexes are distinguishable by the brighter colour of the testes 

 as compared with the ovaries ; the former constitute a single series in 



