Prof. H. Fol on the Family Tintinnodea. 241 



Stein (who is above all preoccupied by the relationship which 

 he supposes to exist between the Tintinni and the Vorticellce) 

 declares that the peristome bears cilia only at its margin — 

 namely, a single row, which descends into the mouth, and in 

 this way represents a dextrogyrous spiral. I am quite ready 

 to believe that Stein had before him an Infusorian thus organ- 

 ized, since he tells us so ; but this animal certainly was not 

 a Tintinnus, and probably belonged to some group allied to 

 the Voriicellce. Another marine form, observed without test, 

 but which this author rightly or wrongly regards as the legi- 

 timate proprietor of certain empty tests found in the produce 

 of the same gathering — another form, I say, is described as 

 bearing on the margin of the peristome an outer row of long 

 cilia, and a single inner row of cilia only half the length. It 

 is difficult to judge whether the author had to do with a Tm- 

 tinnus of which he has given only an imperfect description, 

 or with some quite different genus of Infusoria. In any case 

 Stein's observations were less fortunate than those of Clapa- 

 r^de and Lachmann, to whom the German writer addressed 

 criticisms as severe as they are undeserved. 



If we carefully examine the surface of the disk in the 

 neighbourhood of the mouth, we observe there a slight cres- 

 centiform projection, which rises above the side on which tlie 

 margin of the orifice forms an acute angle (see fig. 3). 

 Are we to compare this projection, with its scarcely indicated 

 outlines, to the part that Stein describes in his so-called 

 Tintinni under the name of " forehead," and compares to 

 the disk of the Vorticellce ? I cannot tell ; but it is certain 

 that the slight swelling in our Tintinni has no relation, near 

 or distant, with the disk of the Vorticellina. 



The nucleus of our Tintinni is very difficult to see. It can 

 hardly be discerned except in famished individuals. More- 

 over I have not paid much attention to this organ, since it is 

 at present demonstrated that the form, the structure, and the 

 number of the cytoblasts varies infinitely more in the different 

 periods of the existence of a single individual than it differs 

 from one species, or even genus, to another. Hence I have 

 some difficulty in understanding how Stein can so much blame 

 Clapar^de and Lachmann for not having described the nucleus 

 in the forms observed by them. Whenever I have thought I 

 could see a nucleus it has appeared to me to be situated near 

 the peristome, in the upper part of the body, and to present 

 an oval form (PI. XVII. fig. 4). Sometimes I have thought 

 that I could distinguish a contractile vacuole in the inferior 

 region of the body (fig. 4). But how is one to arrive at cer- 

 tainty with animals which swim and turn upon themselves 

 Ann. & Mag. N. Hist. Ser. 5. Vol. vii. 18 



