Dr. Henri Blanc on Ceratium hirundiuella. 451 



external horn. The protoplasm thus laid bare had a certain 

 degree of consistency ; and this individual moved rapidly by 

 means of its long flagellum. The above author afterwards 

 mentions having seen two of these individuals in which a 

 part of the skeleton was deficient, united or stuck together by 

 the naked part of their bodies and moving rapidly. M. Bergli 

 cites these curious individuals without knowing what to 

 make either of those joined two and two or of those in which 

 a part of the cuirass is wanting. He does not know whether 

 he is to regard the former as being in conjugation or as indi- 

 viduals in course of division ; he rather believes in a conju- 

 gation ; and as to the second sort, he says of them that they 

 are individuals which have abandoned a part of their cuirass. 

 These few observations of Bergh's confirm mine in every 

 point. This naturalist, when he speaks of individuals united 

 or joined together, has evidently had under his eyes Ceratia 

 which were in process of dividing ; as to the others, of which 

 he speaks as individuals which have abandoned their cuirass, 

 we have only to examine carefully figs. 8 and 9 to be con- 

 vinced that the Ceratium represented in fig. 9 is not an 

 individual which has, so to speak, undergone an incomplete 

 moult, but that it is the product of a division. We have only 

 to remove the right-hand portion of the Ceratium in course of 

 division (fig. 8) to have, pretty nearly, the specimen partly 

 deprived of its cuirass (fig, 9), 



In conclusion, it only remains for me to discuss the question 

 of identity between the Ceratium of the Lake of Geneva, 

 which I regard, like M. Brun, as identical with Ceratium 

 hirundinella^ O. F. Mtiller, and Ceratium reticulatum^ the 

 new species described by Dr. Imliof, and found by him in the 

 lakes of Zurich, Zug, &c. 



I have said in commencing that the skeletogenous membrane 

 of the Geneva Ceratium is produced in the form of horns of 

 different directions and dimensions, namely an anterior one, 

 the largest, and three, or sometimes two, posterior ones, of 

 smaller size. When there are three posterior horns, as in the 

 specimen represented in figs. 6 and 7, the Ceratium of the 

 Lake of Geneva has exactly the form of Ceratium kirundi- 

 nella, O. F. Miill., described and figured by M, Bergh. 

 When there are only two of them (fig. 5) it resembles Cera- 

 tium reticulatumy Imhof. But among the specimens with two 

 and those with three posterior horns I have found others in' 

 which the horn situated outside of the left posterior horn, the 



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