HYDROIDA II 



57 



and oblique nodes; above a transverse joint there is an internodium bearing one or two unpaired 

 sarcothecse in the median line, then the highly oblique joint, and an internodium furnished with a 

 proximal, unpaired median sarcotheca, a large hydrotheea, and two supraealycine pairs of sarco- 

 thecse. Of the supraealycine pairs of nematothecae, the outermost is placed on small projecting apo- 

 physes, the inner pair arises from the internodium on the inner side of these sarcotheca apophyses. 

 All the sarcothecse are mobile. The hydrotheea is very slightly fused with the internodium, the 

 adcladial side has a free portion, in length equal to the hydrotheea opening or a little less, between 

 r / 2 and 3/ 4 the length of the hydrotheea. The hydrotheea is somewhat expanded towards the opening, 

 and is able to accomodate the contracted polyp almost entirely. 

 The gonothecse arise from the stem or the hydrocladia 

 close beneath the hydrothecse. The gonotheca is oval to pear- 

 shaped, as a rule somewhat curved, the males a little more 

 slender than the females. The female gonothecse have basally 

 two sarcothecse, which, (according to Hincks) are lacking in 

 the males. 



Material: 



The Faroe Islands: 6 miles N. by W. of Store Kalso 



depth 60 fathoms 

 Deep hole at the north point of Nolso, — 100 — 

 Boronses 13 miles in N. 75 W. — 30 



The inner pair of supraealycine sarcothecse in Pin mil- 

 iaria Catharina (fig. XXV) appears to have escaped the atten- 

 tion of most investigators; it is probably this pair of sarcothecse nodes in side view. - / inner pair 



of supraealycine sarcothecse. (X 80). 

 which has given rise to the distal median sarcotheca so often 



ascribed to the species. Such median (unpaired) distal sarcothecse I have been unable to find in the colonies 

 at my disposal; not infrequently, however, one or both of the sypracalyeine may have fallen away, rendering 

 it difficult even to trace where they had been. It is remarkable that it should be the inner pair which exhibits 

 such a marked tendency to fall off, exceeding that of the other sarcothecse; the ones in question are, how- 

 ever, also the smallest. In view of the abundance of the present material, and the fact that I found 

 occasion also to investigate material from other parts of the Atlantic, we must regard the statements 

 as to occurrence of an unpaired distal sarcotheca on the hydrotheca-bearing internodium in Plumu- 

 laria Catharina as based on incorrect interpretation of the inner pair of supraealycine sarcothecse. There 

 can be no doubt that the species Plumularia geminata Allman, Plumularia alternata Nutting and 

 Plumularia Clarkei Nutting should be included under Plumularia Catharina, as I have already pointed 

 out in a previous work (1912 p. 4); it is impossible to attach any weight to the characters given for 

 specific distinction when once a larger material has been closely investigated. 



Plumularia Catharina is a southern visitor to the boreal waters (fig. XXVI); round the British 

 Isles it still seems to be of fairly frequent occurrence, but off the coast of Norway it is but little met 

 with, and has only once been recorded from the south coast of Iceland. At the Faroe Islands, the 



The Ingolf-Expedition. V. 7. o 



Fig. XXV. Plumularia Catharina 

 from 6 miles N. by W. of Store Kalso. 

 a. hydrothecate iuternode seen from 

 behind. — b. two successive inter. 



