and Affinities of Graptolites. 



373 



Fiof. 4. 



To the views here maintained further support is given by 

 certain undescribed hydroids in the collections of the United- 

 States Coast Survey placed in my hands for determination. 

 Among these are some plumularians in which that part of the 

 stem which lies at the proximal side of the pinna-bearing 

 portion (and is accordingly destitute of hydrotheca3) carries 

 along its length a single row of fixed nematophores separated 

 from one another by regular intervals, and appearing to take 

 the place of hydrothecae (fig. 4). This part of the hydroid, if 

 detached from the pinnate portion, might (except from the 

 much greater slenderness of both common tube and calicles in 

 the fossil than in the living form) almost be taken for a recent 

 Rastrites. 



Still further, the very im- 

 portant aid aftbrded in such 

 questions as the present by 

 the history of development 

 may be here adduced ; for in 

 the plumularian genus An- 

 tennularia the embryonic 

 stem is provided with well- 

 developed nematophores be- 

 fore any hydrothecce have 

 made their appearance. 



Whether the calicles of the 

 graptolites gave lodgment to 

 true hydranths, or were filled 

 with simple protoplasm, as I 

 have already shown to be the 

 case with the nematophores 

 of the living Plumularidse, it 

 is, of course, impossible to 



h 



Portion of the stem from 

 the proximal side of 

 the pimife in an nn- 

 described plumula- 

 rian from the Gulf- 

 stream, showing the 

 distribution of nema- 

 tophores along its 

 length. 



a a, part of the common 

 canal, with the walls 

 thickened by succes- 

 sive layers of chitine ; 

 b, b, b, nematophores. 



assert with confidence. If, 

 however, we give analogy 

 its full weight, and extend ^^/i 

 the resemblance between the 

 calicles of the graptolites and 

 the nematophores of the plu- 

 mularians to the nature of 

 their contents, we should then 

 have lodged in the graptolite- 

 calicles, not hydranths, but simple masses of protoplasm, 

 capable of emitting pseudopodial prolongations, on which would 

 devolve the duties of conveying nutriment to the colony. 

 The graptolites would thus not merely manifest relations to 



