PENNATUL1DA. 23 



is so deep, that the top is only connected with the other part of the colony by a quite thin string, 

 the top (on the dead specimen) is hanging down like a broken flower along the stem of the colony, 

 and then its rhachis is always prolonged stalk-fashion, most often bent into the shape of an S, so that 

 the top gets a still more independent appearance (comp. fig. 21). Unfortunately, I have had no oppor- 

 tunity of observing the separation itself, the further fate of the separated top, nor that of the 

 remaining part of the colony. 



That I am not here guilty of a misinterpretation of chance mutilation is certain; to be sure, 

 casual injuries are not wanting in many of the specimens in hand, but they have quite a different 

 appearance; here the spicules on both sides of the constriction are placed quite regularly and in such 

 a way as to be evidently arranged for the purpose; broken spicules are never seen as in injuries; 

 moreover, the facts that the constriction always takes place at the same spot, that it is found in 

 different stages and in a somewhat large number of specimens, and further that the top grows in 

 length and emancipates itself, as it were, tend without a doubt to show that this species really is 

 able to separate off the top. Of course it may be doubted whether this is a normal process; but I 

 think it an obvious conclusion to take it to be normal, and to regard the phenomenon as a kind of 

 propagation. The whole individualized character of the top, ready for separation, seems to me to 

 indicate that this part will later live independently as a small colony, develop an interior calcareous 

 axis J ), continue to grow and increase its number of individuals. The rest of the colony, the mother- 

 colony , will then probably form the large zooid at the place of constriction. One single specimen 

 (fig. 24), without any constriction, seems to me of some interest in this connection ; in that place of the 

 rhachis where the constriction is seen in the other specimens, we have here a large, single and median 

 zooid (Z') projecting in a polyp-like manner and interrupting the two rows of smaller dorsal zooids; 

 it is provided with two lateral calyx-points in quite the same manner as the zooid which terminates 

 the rhachis above between the two wings I (Z). The interpretation of this feature might be that the 

 large top-zooid had been formed exceptionally before the constriction, this having not taken place or 

 having been delayed for some reason or other. The specimen in question is otherwise of a good size 

 (27 mm ), has 7 pairs of wings and 3 pairs of rudiments and contains developed sexual organs (even 

 larvte); the calcareous axis reaches only to the height of the pair of wings III, that is to say, to a 

 tolerablv great distance from the spot where the large zooid is formed. 



My conclusion is accordingly, that all the mentioned features of the transverse fission observed, 

 tend to show that this species may justly be called Pennatula prolifrrn. We should then have found 

 a mode of propagation within the Octactinia somewhat reminding one of that known in the Poly- 

 actinia, for instance in Goniactinia prolifera (M. Sars), and the Fungias; but the question, with regard 

 to this sea-pen, is of a transverse fission of a colony. 



Several facts will be more intelligible viewed in this light. In the first place, the circumstance 

 will now be readilv understood why the species was taken in great numbers at both places where it 

 was found, and that, in spite of this, it is only represented by colonies of a youthful character. It is 

 obvious that the colonies need only a slight degree of development to be capable of transverse fission 



■) It might, however, be possible that an interior calcareous axis might come up, before the separation took place; 

 the contrary cannot be said to be proved by the specimens in hand. 



