PENNATULIDA. 27. 



is SO deep, tliat the top is onl\- connected witli tlie other part of the colony b\- a quite thin string, 

 the top (on tlie dead specimen) is hanging down Hke 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 ojapor- 

 tunit>- 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 guilt>- of a misinterpretation of chance mutilation is certain: to be sure, 

 casual injuries are not wanting in many of the specimens in hand, but the\ ha\-e quite a different 

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

 a wa)' as to be evidenth- arranged for the purpose; broken spicules are ne\-er 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 reall\- is 

 able to separate off the top. Of course it may be dotibted 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 independenth' as a small colony, develop an interior calcareous 

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

 colony , will then probabh' 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 maimer 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 haxing not taken place or 

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

 (27™™), has 7 pairs of wings and 3 pairs of rudiments and contains de\'eloped sexual organs (even 

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

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



My conclusion is accordingly, that all the mentioned features of the trans\'erse fission observed, 

 tend to show that this species may justly be called Pninatula prolifera. 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 Fiingi(r\ 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 readily understood why the species was taken in great numbers at both places where it 

 was found, and that, in spite of this, it is onh' represented bv colonies of a \onthfnl 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 contrarv- cannot be said to be proved bv the specimens in hand. 



