224 THE PHENOMENON OF 



by the afternoon ; those not emptied by that time develope 

 no further. Once, however, I saw birth of gonidia occur 

 between six and seven o'clock in the evening; it was on 

 a very dull and rainy day in July, on which the weather 

 suddenly cleared up between five and six o'clock. I 

 have made similar experiments on many other fresh- 

 water Algae ; e.g., on Draparnaldia mutalilis, in which I 

 observed the birth of the active gonidia in March from 

 eight in the morning, in May from six, and the swarming 

 until eleven, A.M., at most. In Stigeoclonium protensum (?) 

 the birth and movement of the gonidia took place in May 

 between six and ten, A.M ; in Chcetophora tuberculata, in 

 August, between eight and two, A.M. ; in Ascidium acumi- 

 natum, in July, from six, A.M. to three, P.M., and even 

 still later, but none so late as dusk. The (Edngoma 

 also ordinarily emit their large gonidia in the morning ; 

 in summer and in bright weather earlier, in winter* and 

 in dull weather later. Since the swarming of the gonidia 

 lasts several hours, in this genus, it may be often observed 

 in the afternoon. In Chlamidococcus pluvialis, both the 

 birth of the first generation of gonidia, and the production 

 of the succeeding generations by division of the earlier, 

 occurs in the morning, after nocturnal preparation, and 

 the same is the case in the formation of new families in 

 the Volvocineae, for instance in Pandorina elegans. What 

 we have here seen in regard to the time of formation of 

 the gonidia of the Alga?, is true also of the vegetative 

 multiplication of their cells. Thus Fockef has observed 

 that the division of the Euastra commences early in the 

 morning, and has advanced so far by evening, that the 

 complementary halves acquire their complete form and 

 full size before night. I have made the same observation 

 in regard to the first commencement of the division of 

 the cells in Spirogyra. For a long time I could not 



* (Edogonium fonlicola, which vegetates all through the winter in the 

 holes in running brooks, and developes the longest filaments at that season, 

 exhibits formation of gonidia oven in winter when brought into the house. 



t 'Physiol. Studien.,' (1847,) p. 47, t. ii, figs. 1,4,5. 



