Peridinium Cypripedium and Urocentrum Turbo. 5 



the same group that the Tintinnoidea border upon. The appa- 

 rently low organization of some of the Peridinisea does not inva- 

 lidate their approximation, through the higher forms, to the 

 Tintinnoidea, any more than the inferior organization of the 

 Cyclopidse depresses the whole class of Crustacea below the level 

 of the group of worms. 



In this connexion I would mention that I do not believe that 

 the so-called Cilio-Flagellata are distinct, as an order, from the 

 Flagellata. I will not deny that the former, as well as the 

 latter, have more intimate relations among themselves than exists 

 between the two groups ; but at the same time there are some 

 (as, for instance, Prorocentrum) among the Cilio-Flagellata which 

 hold their position there by a quite doubtful tenure — the few cilia 

 at the anterior end indicating merely a preponderance in favour 

 of their affiliation with that group, rather than a positive claim to 

 be so united. The lorica gives to Prorocentrum the habit of a 

 Peridinian, and may add a little to the strength of the argument 

 which the cilia afford ; but, on the other hand, there is a new 

 genus of Infusoria which I have described in a recent work* 

 under the name oi Heteromastix {H. proteiformis), which pos- 

 sesses all the habits, actions, mode of progression, and general 

 appearance of a true flagellate infusorian, very much like a 

 Heteromita, Duj., and is endowed with two anteriorly subter- 

 minal flagella — the one acting as a proboscis or tentacular organ, 

 and the other as a trailer or moveable keel ; but at the same 

 time the ventral anterior half of the body is hollowed out by 

 a broad median furrow, which is thickly lined with locomotive 

 cilia — thus presenting a peculiarity not heretofore deemed ad- 

 missible as a characteristic of Flagellata, but, on the contrary, 

 as appertaining alone to the Cilio-Flagellata. 



1 would remark here, moreover, that in view of the fact that 

 Peridinium Cypripedium possesses, beside the median transverse 

 sulcation, an anterior annular furrow, and immediately in front 

 of it a low skullcap-like covering, or pseudo-cuirass (both of 

 which Mr. Carter appears to have been inattentive to in perusing 

 my article), it seems possible that this infusorian may turn out 

 to be generically different from any other Peridinian described 

 hitherto. This looks so highly probable that I will propose the 

 name Peridinopsis for it. 



Since my commentator has gone so far as to doubt even the 

 specific diversity of these two infusorians, I would add, in regard 

 to the species Urocentrum Turbo, that Ehrenberg describes and 



* • Mind in Nature,' by H. Jaraes-Clark, pp. 330, with over two hun- 

 dred illustrations. New York, 1866. 



