4 W. Hofmeister on the Pr'opagation 



tained eight, not globular, but strongly flattened primordial 

 cells. Most, however, passed through the winter-rest unchanged, 

 during which the majority died. At the beginning of April of 

 the next year, the spinous, transparent, outermost layer of the 

 coat was more or less completely decayed on all the spores, even 

 on those which were still to be recognized as living by the vivid 

 green colour of the contents. All the spores still alive contained 

 at least eight, many sixteen daughter-cells, all very strongly 

 flattened, almost discoid. In several spores the outline of the 

 daughter- cells was no longer circular, but displayed two shallow 

 lateral notches. The still-existing, brownish, inner layer of the 

 spore-coat was now seen to be softened ; it no longer exhibited 

 its former' brittleness, and it was difficult to crack it by pressure. 

 Daughter-cells whose lateral constrictions were most strongly 

 marked, were about half as large again as the circular, whose 

 diameter about equalled that of the isthmus of the former, and 

 they almost entirely filled up the cavity of the spore. When 

 these were pressed out from the crushed spore, their form and 

 size agreed almost exactly with that of Cosmarium Meneghinii^. 



I saw similar phsenomena in the spores of Cosmarium undu- 

 latumj Corda, in which the investigation is rendered very difficult 

 by the minute size, and which, cultivated for some months in 

 my room, entered abundantly into conjugation. In this, again, 

 I observed the contraction of the green contents of the cell into 

 a globule occupying the central part ; the division of this ball 

 into two, four, eight, and sixteen spherical masses ; finally, the 

 transition of these daughter-cells of the last generation from the 

 form of circular lenticular bodies into two-lobed ones like the 

 mother-plant. Here the young Cosmaria, whose diameter 

 amounted to scarcely J-th or ^th of that of the mother-plant, 

 were set free by the very gradual solution of the membrane of 

 the spore. A similar process very probably occurred in Cosma- 

 rium tetraophthalmum, but could not be observed there, from 

 the circumstance that all the materials had been used up in the 

 investigation. 



These facts place it beyond doubt that the contents of the 

 spores produced by the conjugation of two individuals of 

 Cosmarium, are transformed by repeated binary division into 

 eight or sixteen daughter-cells, which assume the form of 

 the mother-cell, and finally become free by the solution of the 

 wall of the spore. Such behaviour of the spores had indeed 

 been rendered probable before, by the discovery of the vesicular 

 structure observed by Fockef and KalfsJ, which enclosed a 



* Ralfs, I. c. p. 96, pi. 15. fig. 6. 



t Physiol. Studien, Heft 1. 



X British Desmidiese, p. 164. pi. 27. fig. 2. 



