INVERTEBKATA, CEYPTOGAMIA, MICROSCOPY, ETC. 645 



Anatomy and Histology of the Actiniae.* — In continuation of 

 our account of tlie paper of the brothers Hertv\'ig,| we direct attention 

 to their history of Cerianthus, Edicardsia, and Zoanthus, which is not 

 so elaborate as the preceding portion. 



With regard to Cerianthus, the most important observations are 

 those which deal with the layer of muscles subjacent to the nervous 

 system. Forming bnt a thin layer in the tentacles, they form a more 

 considerable stratum in the oral disk, and here each muscular band 

 has, as a sujiporting lamella, a thin homogeneous layer, which presents 

 a free edge towards the nervous layer, and is, as compared with the 

 same part in the Actinice, much better developed. In the tentacles 

 the elements of the muscular layer are isolated. The middle layer of 

 the body is distinguished by the simplicity of its characters, and the 

 complete absence of si)ecial connective-tissue cells. The endodcrm, 

 also, presents points of diiierence, for its cells are not, as in the 

 Actinice, provided with a single flagellum, but with a tuft of delicate 

 cilia. Parasitic cells are here completely absent. The a-sophagus 

 is, as compared with that of the Actinice, extremely short ; there is 

 only one oesophageal groove, and we are therefore enabled to distinguish 

 a ventral and a dorsal aspect ; when, however, we inquire which is 

 the dorsal and which is tlie ventral, we find that our authors are in 

 opposition to Haacke,"): and that they regard the side on which the 

 groove is developed as being the ventral one. In the walls of this 

 oesophagus there is developed a special muscular lamella. The septa 

 of Cerianthus are only feebly ditferentiated from one another, and this 

 simjjlicity in character extends even to their histological details. After 

 pointing out the leading characters by which they are here dis- 

 tinguished from the Actinice, the writers proceed to an account of the 

 generative organs ; these are very numerous, as they are developed 

 on every septum, at the point at which that process ceases to be 

 invested by the oesophagus ; bath ova and spermatozoa may be found 

 to be enclosed in a capsule of connective tissue, and the testicular 

 follicles are not only set between each of the ovarian but are also 

 found to be aggregated into special bands. 



The most interesting characters in Edicardsia affect the important 

 question of the morphology of the septa ; in these creatures there are, 

 as Quatrefuges showed, only eight septa ; these are all inserted into 

 the Oisophagus, and they are all extremely muscular ; they aro 

 arranged in an exactly symmetrical relation to the two oesophageal 

 grooves. Contrary to what obtains in all allied forms, the tentacles 

 aro not numerically similar to the septa ; in other words there aro 

 more than eight, and the number present is not even always a 

 multiple of that number. 



Passing from these details to a general part, the authors eommenoo 

 with a chapter on the classiticatiou of the Ctelenterata ; to make this 

 cofuplete they aro compelled, after dealing with the systematic rela- 

 tions of the forms already described, to enter upon the relations of 

 these to tlie other Anthozoa, and to an account of the generative 



♦ 'Jen. Zcitsilir. Nutiirwu^s..' xiii. (1S80) p. SfW. t -^ntc, pp. ^.')l-l:.7. 



X Sec this Journal, ii. (.1879) p. 8'J2. 



