Dr. A. Korotneffow Poiyparium ambulans, 209 



upon special lamellar processes of the latter. The direction 

 of the muscular fibres of the ectoderm is parallel to the longi- 

 tudinal axis, and in the bu«cal cones vertical. Where the 

 latter pass into the buccal disk the fibres acquire the above- 

 mentioned direction. 



This description of the structure of a portion of the wall of 

 Poiyparium proves indisputably that in it we have to do with 

 an Actinia ; in both instances we find points of approximation 

 common to them and the other Coelenterata^ or more properly 

 the Hydroida and Siphonophora. So far as I know this 

 attempt has not hitherto been made, and we are quite in the 

 dark on the subject. In my former memoir upon the his- 

 tology of the Siphonophora * I endeavoured to show that 

 cnidoblasts, sense-cells, and nerve-cells are not only altered 

 epithelial cells, but that, when we have to do with animals 

 (such as the Siphonophora, for example) in which an epi- 

 thelial muscular system occurs, these have a direct genetic 

 relation to the muscular fibrils, and therefore are to be regarded 

 as altered muscle-cells. According to this an embryonal cell, 

 after it has separated off one or more muscular fibrils, acquires 

 quite a different specific function, and becomes converted into 

 weapon-, gland-, or sense-elements. If we adhere to this 

 principle, it becomes a question in what manner the Actinia- 

 structure is to be referred to this type. In the Siphonophora, 

 especially in Forskalia^ we see that a nerve-cell, or rather a 

 nerve-muscle-cell, scarcely separates from the epithelia, and 

 lies directly applied to the latter ; in the Actinia this process 

 has gone further — here the nerve-cells have fallen low down 

 and formed a special layer ; but this stands in immediate 

 relation to the muscular fibrils which cling to them. To a 

 certain extent a genetic relation between the muscle- and 

 nerve-layers is to be seen in Poiyparium ambulans, inasmuch 

 as the muscle-layer possesses no cell-nuclei. The smooth 

 non- varicose form of the muscular fibrils leads to the belief 

 that the nuclei of the muscle-cells have not become assimi- 

 lated to the muscular fibrils, but are to be sought elsewhere ; 

 hence I see no impossibility in the assumption that the cells 

 of the nerve-layer are to be regarded, not as true nerve-cells, 

 but as nerve-muscle-cells, or, otherwise, as metamorphosed 

 muscle- cells. 



Now if we bear in mind that in the Siphonophora the 

 relation of the cnidoblasts to the muscular fibrils is very 

 intimate, and that in it we find a whole series of progressive 

 transformations, the extreme form of such transformation, 



* Korotneft^ "Histologie der Siphon ophoren," in JNIitth. Zool. Stat. 

 Neapelj Baud v. 



