444 Dr. Henri Blanc on Ceratlura lilrundinella. 



XLT. — Note on Ceratium hlrundinella (0. F. 3IuUer), its 

 Variahility and Mode of Reproduction, By Dr. Henei 

 Blanc*. 



[Plate XII. figs. 4-9.] 



In tlie ' Compte Eendu ' of the meeting of the Society 

 de physique et d'Histoire naturelle de Geneve, on the 17th 

 April, 1884, p. 545, Prof. Brun cites among the pelagic 

 vegetation collected in the spring in Lake Leman, near 

 Geneva, a Cilio-flagellate, Ceratium hirundinella, Bergh, 

 synonymous with Ceratium macroceras^ Schr. Without 

 adding further details, the author of the communication says 

 that this Peridinian, which is furnished with a strong siliceous 

 envelope, has occurred pretty abundantly several times. 



Nearly at the same time Dr. Imhof published (Zeitschr. 

 fiir wiss. Zool. Bd, xl. Heft i.) the results of his researches 

 upon the pelagic fauna of the Swiss Lakes, and, among other 

 new species, described a new Cilio-flagellate which he bap- 

 tized with the name of Ceratium reticidatum. 



Knowing the uniformity which exists in the faunas of our 

 different Swiss lakes, a uniformity which may be so fre- 

 quently recognized in the numerous investigations made by 

 Prof. Forel, I tried to discover in the pelagic fauna of the 

 Lake of Geneva the species of Ceratium indicated by Prof. 

 Brun and the new species described by Dr. Imhof. 



In the produce of my very first fishing, performed on a fine 

 day towards the end of May, I found in abundance, at a depth 

 of 10 metres, Ceratium Mrundinella^ O. F. Miillerf, and 

 Ceratium reticidatum^ Imhof, in company with another Cilio- 

 flagellate, which, I think, has not yet been mentioned as 

 living in our Swiss lakes, namely Glenodinium cinctum^ M. 



More than this, a considerable amount of material enabled 

 me to ascertain that Ceratium Mrundinello., like the other 

 species of Ceratium so carefully studied by M. Bergh |, pre- 

 sented a great variability of form, and that, in reality. Dr. 

 Imhof's new species was not distinct, but rather formed part 

 of the cycle of this variability. 



Before discussing the question of identity between Cera- 

 tium reticidatum and C. hirundinella ^ I will give some details 

 as to the organization of this Cilio-flagellate of the Swiss 



* Translated from the ' Bulletin de la Societe Vaudoise des Sciences 

 Naturelles/ ser. 2, vol. xx. pp. 305-315, pi. x. (February 1885). 



t To avoid confusion, I ahvays adopt, as the author's name, that of the 

 naturalist who first described the animal referred to. 



+ Bergh, " Der Organismus der Cilioflagellaten. Eine phylogenetische 

 Studie," Morphol. Jahrb. Bd. vii. Heft 2 (1881). 



