250 BULLETIN OF THE 



appears to be, then, a structure which we may look upon as a -rudimentary 

 hydrotheca ; moreover, this view receives support from the position of these 

 processes, that is, at the bases of the hydrotheca-bearing portions of the colony, 

 with the contents of the hydrothecse in immediate connection with that of 

 these basal processes. 



After the very valuable suggestions of Professor Allman * on this point it is 

 not difficult to conceive that the pinnae of N. grandis may at one time have 

 borne only oval processes of a large and peculiar tj'pe, much like the oval basal 

 processes now found on the bases of the pinnae, and that these have been grad- 

 ually developed into true hydrothecae. The development of the upper comere 

 of the cauline nematophores indicate how the supra-calycine nematophores 

 may have been produced. 



The contents of one of the mesial nematophores with its extruded protoplas- 

 mic processes has been so well preserved that I have been able to get an accu- 

 rate camera-lucida sketch of it (Plate V., Fig. 35). It has the same structure 

 apparently as those figured by G. 0. Sars t in his Lafoeina tenuis. 



* Gymnoblastic Hydroids, Eay Societj-, p. 176 et seq. Hydroids of the Gulf 

 Stream, in Mem. Mus. Comp. Zool. Yol. V. No 2, p. 51. 



t Bidrag til Kundskaben om Norges Hydroider, Af G. 0. Sars. Tab. V. Figs. 4, 5. 



Cambridge, January 10, 1879. 



