ACTINIAR1A 



In 1893 I have given a detailed description of this interesting, very primitive species, and therefore 

 I here only add some statements especially concerning the size and distribution of the stinging capsules. 

 The spirocysts in the ectoderm of the column are very numerous, their size variates from about 22 X 2,5 p 

 to 43 x 5 p. In the tentacles they are of about the same size as in the column, and numerous in the prox- 

 imal part, but sparse in the apex, which condition evidently is correlated with the unequal occurrence of 

 the nematocysts in these parts (compare below). In the ectoderm of the actinopharynx I have not found 

 any spirocysts in maceration-preparations. In my description of the species 1893 I have also expressed my 

 suspicion that the very few spirocysts I observed in this part probably are not normal components of the 

 actinopharynx. In the ectoderm of the column the nematocysts are numerous and partly of a smaller type 

 17 22 x 1,5 fj., partly of a larger one 29 50 X 3 3,5 //. In the latter the basal part of the spiral thread 

 is often discernible. Furthermore I have seen a few nematocysts with the thread thrown out. These cap- 

 sules were of larger dimensions (60 80 x 4 4,5 ft). In the tentacles I have also observed nematocysts of 

 two unequal dimensions, partly 19 24 X 22,5 . partly 44 58 X 3,5 4 //. The former are rather nu- 

 merous, the latter very much so in the summit of the tentacles, where they are closely packed together, so 

 that they completely intercept the view of all other nematocysts and cells, hereby causing the distal part 

 of the tentacles to form strong stinging batteries. Further down on the tentacles these capsules are more 

 sparse, although also here they generally occur, the spirocysts at the same time appearing in greater num- 

 bers. The nematocysts of the actinopharynx are rather common and comparatively small (22 31 X 2 2,5 ft). 

 Sometimes I have also here observed such large nematocysts as in the tentacles, but probably 

 they have only been attached to the actinopharynx and belong to the tentacles. The basal part 

 of the spiral thread is often discernible in the nematocysts of the actinopharynx. In expanded as 

 well as sometimes in contracted state small papilliform elevations on the column are to be observed 

 ("weissliche Flecke" Carlgren 1893) almost as in Sideractis, though here perhaps not so distinct. 

 In these places the ectoderm is a little thickened, I have, however, not found any real difference in 

 the structure of the ectoderm of the papilliform elevations and of that of the grooves between them. 

 The shallow furrows are not always distinct, especially when the actinopharynx is expanded. In larger 

 specimens I have noticed a greater number of tentacles than before stated by me. 



Genus Gonactinia M. Sars. 



Diagnosis: Gonactiuiidae with smooth, cylindrical column. Margin not undulated. Longitudinal 

 muscle- and nerve-layer well developed. Tentacles long, few, at the base not constricted, not swollen 

 in the apex. Oral disc flattened or conical. Perfect mesenteries 7 10, commonly 8 (the Edwardsia-mesen- 

 teries"). The stronger mesenteries differentiated in filament-mesenteries and genital-nlameut-mesen- 

 teries. The weaker mesenteries without filaments. Arrangement of the mesenteries often irregular, probably 

 in connection with the reproduction by transverse partition. 



