ACTINIARIA 



. 213 



the mesenteries diffuse. Parietobasilar muscles differentiated, much expanded on the mesenteries. Basilar 

 muscles with rather numerous, closely packed, high folds. Oral stomata present. Marginal stomata as a rule 

 on the stronger mesenteries. Nematocysts in the ectoderm of the tentacles 19 34 x 2,5 ft, in the actino- 

 pharynx 24 31 X 2,5 p, here also nematocysts with discernible basal part to the spiral thread 24 29 X 5 //. 

 Spirocysts in the ectoderm of the tentacles of variable size 22 X 2 to 55 X 5 . 



Colour in alcohol white, oral disc brown, actinopharynx dark brown. 



Dimensions of the largest specimen, length 4cm, breadth 4,5cm. 



Occurrence: Davis Strait. 6635' N. 56^' W. 318 fms. Bottom temp. 3,9. (Ingolf-Exp. St. 32) 



8 spec. 



Danmark Strait. 6434' N. 3ii2' W. 1300 fms. Bottom temp. 1,6. (Ingolf-Exp. 

 St. n) 4 spec. 



Exterior aspect: The form of the body varies rather considerably, according to the different 

 state of contraction of the animals, now it is strongly flattened (PI. 3 fig. 2) now more cylindrical (PI. 3 fig. 3). 

 The pedal disc is wide, the column smooth and irregularly sulcated, in the uppermost part, in certain specimens, 

 with longitudinal furrows, surpassing the limit of the mesogloeal bridges of the tentacles. Neither a fossa 

 nor a distinctly marked margin are present. The tentacles on the outside display very large thickenings 

 of the mesogloea, prolonged far upwards. The distal part of the tentacles is conical or cylindrical with a 

 small aperture in the apex. In some tentacles the apertures are very large, but they are artificial, due to bad 

 preservations. The tentacles are about 64 to 68, arranged in several cycles and thinly scattered. Owing to the 

 strong contraction of the animals I have not been able to determine their arrangement. The tentacles may be 

 totally covered by the column. The oral disc is wide, provided with radial furrows and, in the state with 

 involved tentacles, strongly excavated. The greater part of the oral disc bears tentacles. The actinopharynx 

 is not long, longitudinally sulcated and provided with two broad, symmetrically placed siphonoglyphes. 

 These latter have well developed aboral prolongations and in the oral region two distinct gouidial tubercles. 



Anatomical description. The ectoderm of the column is almost totally lost in all specimens. 

 In a specimen there remain just above the pedal disc some fragments, containing very numerous nematocysts, 

 17 19 X 2 n large; the mesogloea was very thick, cartilaginous and unequally structured in the outermost 

 and in the inner parts. The former is namely provided with numerous cavities, containing cells, while the 

 latter are of more typical appearance with scattered protoplasma-poor cells. Unfortunately I cannot give 

 a good description of the former as the mesogloea was not well preserved. 



The endodermal circular muscles are rather weak, the mesogloeal sphincter of some specimens rather 

 strong, of others, as well as of the largest specimen, weak. In the latter case it only occupies a small part 

 of the breadth of the mesogloea, in the former it is about half as broad as the mesogloea. Also in one and 

 the same specimen the strength of the sphincter may vary in different parts, possibly owing to a different 

 contraction of the tissue. The sphincter is rather elongated and gradually passing into the circular muscles 

 of the endoderm. It is close by the endoderm and shows no distinct longitudinal stratification, though the 

 muscles seem to have been enclosed in the mesogloea during different periods. The meshes are small and 

 arranged in groups, surrounded by somewhat broader balks of the mesogloea (textfig. 201, transverse 



