Prof. H. Fol oa the Family Tintinnodea. 249 



Cyttarocylis cassis. 



Dictyocysta cassis, Hackel. 

 (PI. XVII. fig. 6.) 



Test excavated at the surface with deep pits formed only 

 by a delicate membrane, irregular, at least twice as large in 

 the neighbourhood of the orifice as in the region of the apex ; 

 conical, suddenly widened out near the aperture. 



Animal conical, attached by a peduncle to the apex of the 

 test ; peristome bearing twenty rows of cilia. Surface of the 

 body smooth. 



Length of the test 0'117 millim. ; width at the orifice 

 0-078 millim. 



It is in this genus, no doubt, that Tintinnus denticulatus 

 and T. Ehrenhergii, C. & L., will have to be placed. 



We reserve the name of Dictyocysta for the species in which 

 the test is really perforated and reduced to a sort of open cage, 

 such as Dictyocysta elegans, Ehr., D. mitra, Hack., D. lepida, 

 Ehr., D. acuminata, Ehr., D. templum, Hack., and D. tiara, 

 Hack. 



As to Tintinnus fluviatilis, Stein, I have already expressed 

 the opinion that it is not a Tintinnodean at all. The family 

 Codonellidge is differentiated by the small shreds of the margin 

 of the peristome, although the tests very closely resemble those 

 of the genus Coniocylis. 



The relationship of our family is sufficiently indicated by 

 the peculiar structure that I have described. It is clear that 

 their relationship to the Vorticellina of which Stein speaks 

 has no existence, and that our Infusoria differ still more from 

 the Vorticelloi and Stentors than these do from each other. I 

 shall not discuss the question whether the Tintinnodea should 

 enter into the order Peritricha ; for that order seems so little 

 in accordance with nature that it can hardly be maintained. 

 Stein himself seeks in vain to find a character common to all the 

 families of which he composes this heterogeneous order. The 

 definition that he endeavours to give of it degenerates into a 

 casuistical statement in which the characters of all the families 

 are enumerated, making the profound differences which separate 

 them still more striking. If, notwithstanding, our author 

 finds " an incontestable air of relationship " in all these 

 creatures, this is an affair of sentiment ; and this sentiment we 

 are perfectly free not to share in. 



