ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 435 



tliis meridian there is nothing between the external ectoderm and the 

 oesophageal ectoderm but the supporting lamella ; the result of the 

 movement is that the endoderm in the place of the first mesentery is 

 pulled down ; the oesophagus now grows downwards in the meridian as 

 a lobe of ectoderm, which represents the first filament. The filament, 

 like the oesophagus above it, rests on the supporting lamella, and is 

 consequently flush with the surrounding endoderm. The second fila- 

 ment is formed on the opposite side of the animal in the same way as 

 the first. After this the formation of mesenteries as such begins; the 

 oesophagus withdraws from the body ectoderm along the line of the first, 

 and subsequently of the second mesentery, remaining connected with it 

 by the supporting lamella, which narrows to a thin band. The two 

 intermediate chambers thus formed are at first solid. Below the oeso- 

 phagus the endoderm forces its way under the short filaments, forming 

 very slight ridges, with an axial band of supporting lamella ; these 

 ridges are the mesenteries, and on them the ectodermic lobes, or filaments, 

 rest. When the two intermesenteric chambers are hollowed out the 

 formation of the second pair of mesenteries with their filaments begins. 

 The incomplete mesenteries of the larva are successively supplied with 

 filaments by the reflection and upward growth of the ectoderm, and it is 

 very probable that the incomplete mesenteries of the adult are so 

 supplied in the adult. 



In the older larvae studied by the author the filaments are quite 

 simple, and the cells are continuous with the endoderm of a thin 

 mesentery. In the adult the edge of the mesentery is considerably 

 enlarged, and forms two rather definite tracts, between which the filament 

 proper rests. The author thinks that the very elaborate division of the 

 filaments into three tracts physiologically distinct, made by the Hertwigs, 

 cannot be considered as typical. 



Mr. Wilson agrees with Koch, Fowler, and Bourne, in regarding the 

 skeleton as a pure ectodermic structure, which is morphologically 

 outside the body. With reference to the recent observations of Gbtte on 

 the embryology of Amelia, and his proof that the Scyphostoma larva, with 

 its ectodermal oesophagus and four complete mesenteries, is of an 

 Anthozoan nature, Mr. Wilson urges that his observations dispose of the 

 view that what is seen in Aurelia is typical of the Anthozoa ; he thinks 

 that the symmetrical method has been derived from the gradual method 

 seen in Mancinia, and he suggests that it may be connected with the 

 reduction of the mesenteries to four. He is the more inclined to believe 

 this, as an individual variation, seen in several larvae, suggests the 

 manner in which the condition found in Aurelia has been brought about. 



Gorgonidae of Naples.* — Dr. G. v. Koch commences his monograph 

 on the Gorgonidas of the Bay of Naples with some remarks on the 

 structure of Alcyonarians in general. With regard to the mode of 

 formation of colonies he points out that the stolons may arise only at 

 the base of the polyp, and may be simple, as in Cornularia, or fused into 

 basal plates as in Bhizoxenia and Gorgonia, or they may arise at 

 different points of the polyp ; these may be simple or fused into plates, 

 as in Telesto, Pennatula, and Gorgonia, or the stolons may be irregular 

 and fused into a massive tissue, as in Alcyonium, Corallium, and Sclero- 

 gorgia. There may be no skeleton as in Moxenia, or an investing ecto- 



* Fauna u. Flora des Golfes von Neapel, Monogr. xv. (1887) 97 pp. (10 pis.). 



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