INVEETEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 643 



regarded as digestive organs owing to the same ocenrrencc in 

 their ordinary entoderm cells, thus explaining Lewes and Kruken- 

 berg's observations of the complete absence of any free digestive 

 secretion ; on the other hand, the Hert wigs' interpretation of the 

 abundant gland-cells which abound here, must be rejected, and they 

 must be regarded instead as mucus- glands. The Coelenterate ento- 

 derm cells are ranked among the araceboid epithelia, taking in as they 

 do, their food by pseudopodia-like processes ; this is well seen in 

 Praya diphyea, whose cells are long and envelope food-particles in a 

 Plasmodium, formed of the fused pseudopodia ; a similar fusion of the 

 ends of the cells occurs in the Ctenophora and Adinice. In Cteno- 

 phora the food-particles pass into the wandering cells of the mesoderm, 

 as in sponges. 



Considering that representatives of all the chief groups exhibit 

 this phenomenon, it would appear to be a primitive endowment of the 

 Ccelenterate type, and — the same being the case with the lowest worms, 

 the Turbellarians — also of the Metazoa in primitive times. As the 

 method does not demand a sjiecial digestive cavity, this last would 

 appear, where present, to be of secondary origin. 



Probably some points in the development of Coelenterata, which 

 as yet appear at variance with the gastrsea-theory, may be explained 

 by these considerations. 



Nervous System of Beroe.* — Dr. Eimer recajntulates the present 

 condition of our knowledge of the nervous arrangements in the 

 Coelenterata. He points out that in an earlier work he had 

 insisted on the fact that the nervous system of Beroe ovatus was 

 not distinctly localized, but was represented by a number of nerve- 

 cells which were distributed over the whole surface of the body, and 

 were numerous only in the region of the anal pole ; no true nerve- 

 cords, such as are seen in the higher animals, are to be found in this 

 Ctenophore. Very similar results have been shown among the Meduste ; 

 here there is a lamellar central nervous system distributed over the 

 body, and attaining its greatest development in the Craspedota in the 

 region of the margin of the umbrella (Cycloneura), and in the Acras- 

 pedota in the region of the marginal bodies (Toponeura). In both 

 these groups the nervous elements may be frequently connected with 

 the epithelium. In these, just as much as in Beroe, it is difficult to 

 distinguish the nerve-cells as morphological elements, but this is, of 

 course, in complete agreement with the a priori consideration that 

 characteristic tissues are no more suddenly developed than are distinct 

 fimctions. Pliysiological experiments on the Medusa? have confirmed 

 these views : it now remains to apply the same test to Beroe. 



Experiment A. — Specimens were so operated on as to divide them 

 into three equal parts, representing rcspcctivuly the anal polo, the 

 oral pole, and the median portion of the body ; wlicn this was done 

 it was foinid that all the ctcnophores ceasod their activity; after a 

 sliort time, however, this again reapi)eared in the parts connected 

 with the anal pole ; after four hours nearly all the parts wore in 



* ' Ar.-l,. Mikr. Annt..' xvii. (Is7!)) p. 2VX 



2 r 2 



