1881.] 



MICKOSCOPICAL JOUKNAL. 



223 



sentation, which, if it be one of the 

 smaller Naviculae may too often 

 equally well represent many other 

 forms, and, finally, to coin some 

 unpronounceable word, or immor- 

 talize some friend, and sends forth 

 the bantling ; since nobody can ven- 

 ture to question its legitimacy, for 

 does it not differ somewhat from 

 every form hitherto figured or de- 

 scribed in outline ? And has it not a 

 few more or less striae in .001 of an 

 inch. I shall be very sorry if, in what 

 I have said, I am considered as cen- 

 suring men who are unquestionably 

 hard-working and conscientious stud- 

 ents of these interesting little organ- 

 isms, I am only regretting that, in- 

 stead of laboring to reduce the gen- 

 era and species of the Diatomaceae, 

 and seeking for broader and firmer 

 principles to guide in their study and 

 classification, so many worthy per- 

 sons are contented to accept trivial 

 distinctions as of generic and spe- 

 cific value, and they are so encumber- 

 ing the subject, that some day it will 

 be crushed by its own dead weight, 

 giving place to a new structure, util- 

 izing as far as possible the ruins, but 

 erected upon a more solid foundation. 



Is it Tintinnus ? 



BY C. M. VORCE, F. R. M. S. 



In Dr. Leidy's work on Rhizopods, 

 on plate XII, figs. 19, 20, 21, and on 

 plate XVI, fig. 35, are figured what is 

 there called Difflugia cratera ; under 

 this name it is described on page 108. 

 Appended to the description, and to 

 the list of the figures on plate XII, is 

 a foot-note in substance as follows : 

 " Since writing the above it has oc- 

 curred to me that these forms may be 

 the shell of a ciliated infusorian of 

 the genus Tintinnus T It appears 

 also, from the description of the spe- 

 cies and of the plates, that all of the 

 specimens figured by Prof. Leidy were 

 dead shells, two of which were from the 

 water-supply of Buffalo, N. Y. This 

 shell has for years been common in 



summer in the water-supply of Cleve- 

 land, Ohio, but until quite recently I 

 have not seen it alive or heard of its 

 being so observed. It has always 

 been called here a Difflugia. 



This summer Dr. Robert Dayton, 

 of this city, in speaking of the forms 

 in our water-supply, mentioned this as 

 a free swimming form, at which I was 

 somewhat surprised at first, having so 

 often noticed it and never having seen 

 it move, but soon afterward he exhi- 

 bited to me an individual of this species 

 which was not only alive but active. 

 This specimen was somewhat shorter 

 and more robust than Leidy's fig. 35 

 on plate XVI, and with the apex 

 slightly more pointed, but it is un- 

 doubtedly the same species. It was 

 attached by the edge of the lips of the 

 shell to a mass of green, vegetable de- 

 bris, and alternated periods of quiet- 

 ude with periods of vigorous thresh- 

 ing up and down, as if trying to break 

 loose from its attachment, which, 

 however, must have been voluntary, as 

 the edge of the shell was in but the 

 very slightest contact with the mass 

 to which it adhered. 



While it rested, the mouth of the 

 shell was uppermost, and the observer 

 looked directly down into the interior 

 of the shell. In this position there 

 was visible a strong vortex current in 

 the water over the mouth of the shell, 

 but not within it, so far as the visible 

 particles in the water would indicate, 

 for these were plainly seen, both in a 

 top view and afterwards in side view, 

 to pass directly across the mouth of 

 the shell, barely passing below the 

 level of the edges. The vortex pro- 

 duced by this species is very peculiar, 

 and quite different in character from 

 that produced by a Rotifer or a Vorti- 

 cella : the movement of the particles 

 in the water is slower and steadier, and 

 the acceleration of speed as they ap- 

 proach the shell is less noticeable; they 

 pass steadily across the mouth of the 

 shell, ail moving in one direction, and 

 sail quietly away on the other side, 

 not often returning in a circle to pass 

 through the vortex again and again, as 



