ACTINIARIA 



45 



middle line between the insertions of the mesenteries. On transverse-sections two or exceptionally some more 

 nemathybomes may simultaneously be hit in the middle line. Also in 3 expanded specimens (from Faernes, 

 Lyngen (textfig. 18) and Davis Strait) I have observed the same irregular arrangement with sometimes 2 

 or a few more nemathybomes besides each other. In strongly contracted individuals the nemathybomes appear 

 very indistinctly, so that the scapus seems to be smooth. The capitulum is short, smooth, with shallow, 

 mesenterial furrows. It is not provided with papillae (nemathybomes?) as Danielssen says. The number of 

 tentacles is generally 12 which I have observed in a great number of specimens; I have found 13 tentacles 

 once, 14 three times and 15 once. In the specimen from Bredefiord one tentacle was provided with an off- 

 shoot at the base, another one was bifurcated, circumstances which are probably connected with a regeneration. 

 The inner tentacles are as usual inEdwardsia shorter than the outer ones. The oral disc is small, the mouth 

 oval. The actinopharynx is provided with 8 longitudinal furrows, a distinct ventral siphonoglyphe is present. 

 Anatomical description: The ectoderm of the physa is of ordinary height with sparse, scattered 

 nematocysts, about 12 /t long. In contracted specimens the mesogloea is in the periphery of the physa thicker 

 than the ectoderm, thinner in the centre of it. Its endoderm is higher than its ectoderm and rich in vacuoles, 

 as is usually the endoderm of the column. The periderm and the ectoderm of the scapus are thin. The nema- 

 thybomes are rather large and, especially in the distal part of the column, provided with numerous, often a 

 little curved nematocysts. Their size varies between 48 and 67 x (3) 3.5 4ft. The following table shows 

 the size of the nematocysts of a series of specimens: 



The endodermal, circular muscles are well-developed. The ectoderm of the capitulum is high and 

 provided with numerous, about 10 12 ft long, thick-walled nematocysts. At the base of the ectoderm there 

 is a well-developed layer of nerve-cells and fibrillae which Appellof (1893) was the first to observe and re- 

 produce. The' nematocysts of the tentacles are numerous, (concerning their size compare the table!), the 

 spirocysts vary from 12 X I 1.5 u to 26 X 2.5 3 ft. The longitudinal muscles of the tentacles and the 

 radial muscles of the oral disc are well-developed. The ectoderm of the actinopharynx is high in the ridges, in 

 the furrows lower, its nematocysts numerous. The siphonoglyphe is distinct and provided with longer cilia 

 than the other part of the actinopharynx. 



The imperfect mesenteries in the most distal part of the body are comparatively well-developed. If 

 only 4 of these are present, they are found in the lateral and ventro-lateral "Edwardsia"-compartments 

 (textfig. 9). The longitudinal muscle-pennons (textfigs. 40 42) of the 8 perfect mesenteries are strong, in 

 transverse sections through the reproductive tract rather elongated and provided with some twenty to some 



