Dr. Henri Blanc on Ceratium hirundinella, 447 



M. Bergh * gives no details as to the protoplasm and the 

 nucleus of Ceratium hirundinella, and contents himself with 

 saying : " As regards the protoplasm, cell-nucleus, &c., this 

 form appears exactly to resemble Ceratium cornutumJ^ Ac- 

 cording to this author therefore the nucleus of Ceratium hirun- 

 dinella is elongated with its longer axis parallel to the longer 

 axis of the animal, and does not contain any nucleolus. If 

 these facts were well established I admit that it would require 

 a great exertion of the imagination to confound under a single 

 species the Ceratium found in the Swiss lakes and the Cera- 

 tium hirundinella of O. F. Miiller. But the same author 

 takes care to add further on, in speaking of the latter form : — 

 " Of this form (in opposition to that above described) I have 

 observed only a few individuals, and therefore I am unable 

 to state anything as to its variability ; nevertheless the 

 material was sufficient for me to determine the homologies 

 and the systematic position of this freshwater form." It 

 appears clearly from this phrase that M. Bergh, having a 

 deficiency of material, has chiefly attended to the external 

 form of the animal, neglecting to study its protoplasm and 

 nucleus ; this author, therefore, must not take it ill if I regard 

 what he says upon this subject as only a simple supposition. 



Although I have had under my eye several dozens of 

 Ceratia I have never been able to discover a contractile 

 vesicle — an observation which, moreover, is in accordance 

 with those made by M. Bergh and others. 



In describing the skeletogenous membrane I have stated 

 that it is interrupted on one of the surfaces of the body, the 

 ventral surface, and that it bounded a large groove ; from the 

 bottom of this groove, when we observe living animals, there 

 issues a flagellum (fig. 6,/), sometimes as long as the body, 

 which strikes the water, keeping generally a posterior posi- 

 tion, while the animal always moves in the direction of the 

 anterior horn. If the existence of this long flagellum is not 

 difficult to establish, it is otherwise with the circlet of vibra- 

 tile cilia, w^hich, according to the authors who have paid 

 attention to the Cilio-flagellate Infusoria, is placed below one 

 of the margins of the cincture. I have never been able to 

 observe any such circlet of cilia in living specimens, or in 

 others treated with reagents. Nor have I been able to recog- 

 nize the presence of the two flagella which, according to the 

 recent observations of Dr. G. Klebs f, replace, in the Ceratium 



* Bergh, loc. cit. p. 216. 



t G. Klebs, '* Ueber die Organisation einiger Flagellaten-Gruppen und 

 ihre Beziebungen zu Algen und Infusorien," in Untersucbungen aus d. 

 botan. Inst, zu Tiibingen, Bd. i. Heft 2 (Leipzig, 1883). 



