ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 513 



acquaintance with the observations of Pourtales. Mr. Carpenter is 

 convinced that D. parfaiti is the same as Wiizocrinus rawsoni. The 

 fragmentary condition of the arms is nothing unusual, as these arms 

 often break off at one of the syzygies ; their absence, therefore, must 

 not be taken as a proof of the feeble development of the arms. 



In another note * Mr. Carpenter discusses the statements made by 

 some observers as to the absence of the basals in certain Neocrinoids, 

 and gives reasons, based on morphological considerations, for believing 

 that they are really present ; their absence would lead us into many 

 grave difficulties. 



Ccelenterata. 



Structure of Hydroid Polyps.f — In this, his second, essay C. F. 

 Jickeli deals with the histological structure of Tubularia, Cordylophora, 

 and other Hydroids ; commencing with an account of T. mesemhry- 

 antJiemum, attention is directed to the existence of two whorls of arms 

 on the hydranths, but, as the author is as yet unable to come to any 

 decision as to their morphological value, he speaks of the one nearest 

 the mouth as the first, and the other as the second whorl. The 

 number of arms presents marked individual variations. Among the 

 ectodermal cells are those which are ganglionic ; not numerous, they 

 are generally, though not always, poorly provided with protoplasm ; 

 most of them are bipolar, and their processes are generally set parallel 

 to the muscular fibres. A detailed account of this form is followed 

 by some observations on Cordylophora lacustris, Cladonema radiatum, 

 Coryne grceffii n. sp., which was found in an aquarium of the Zoolo- 

 gical Station at Trieste; Gemmaria implena, Perigommius steinachi 

 n. sp., Podocoryne carnea, Campanopsis sp., Lafoea parasitica, Campa~ 

 nularia coliculata, Obelia plicata, Anisocola halecioides, A. setacea, 

 Isocola frutescens, and KircJienhauria sp. 



Sixteen genera have now been examined by the author. In Hydra 

 he finds an ectoderm separated by a supporting lamella from the endo- 

 derm, while the gastric cavity is directly continued into the arms. 

 This simple condition is not, as Allman has shown, to be found in any 

 other polyp, for in all others there is a greater development of the 

 intermediate tissues ; these last may, in the Tubulariidee at any rate, 

 be spoken of as a third body-layer, though one cannot definitely call 

 it a mesoderm ; with regard to the development of this layer, we 

 unfortunately know nothing certain. 



In the ectoderm there are to be found investing cells which often 

 become epithelio-muscular, and rarely supporting, glandular cells, 

 various kinds of stinging cells, cells which go to form the capsules of 

 the urticating cells, flagellate elements, ganglionic and sensory cells. 

 The first of these vary considerably in size, and when they diminish 

 in height it is often found that the boundaries between the cells dis- 

 appear, and the whole fuse to form a lamella, on the lower surface 

 of which a layer of fibrils becomes differentiated. The musculature is 

 always best developed on the arms ; the supporting cells are best 



* Tom. cit., pp. 327-34. 



t Morph. Jahrb., viii. (1883) pp 580-680 (4 pl8.). 

 Ser. 2.— Vol. III. 2 L 



