Cocconeis, Cymbella, Auiplioia mid Anipliipliora. 3 



The spore is formed by two of the smaller frustules, one of 

 which is less in size than the other (fig. 13). These, after having 

 become approximated, first secrete around themselves a mucus 

 in which they are thus imbedded. The commencement of the 

 sporangial frustules is then indicated by two elliptical masses of 

 endochrome api)earing in the midst of this, parallel to and be- 

 tween the conjugating frustules (fig. 11); at least this is the 

 earliest part of the process which 1 have observed. The spo- 

 raugial frustules in which the endochromes are enclosed re- 

 spectively, then become elongated (fig. 15) ; the transverse lines 

 appear, the endochromes become scattered over their new habi- 

 tations (fig. 17), and at length the frustules are formed (figs. 18, 

 19). By this time the mucus-investment and the valves of the 

 conjugating frustules, which separate during the process, are 

 thrown ofi", and the new frustules are thus liberated. The large 

 conjugating frustule bears to the sporangial frustule (fig. 20) the 

 proportion of ^i^ to ^^j of an inch ; at least, these are their re- 

 spective measurements. 



Amphora oralis (Kg.), mihi. On the 31st of July, after a mass 

 of that interesting form of Spirogrjra, whose cells after division 

 conjugate with each other, had sporcd and sunk to the bottom 

 of the basin, with an Oscillatoria which was also present, several 

 species of Diatomea? multiplied upon the sides of the basin, 

 among which were many frustules of Amphora of different sizes 

 undergoing deduplication and conjugation. 



The spore is formed by two of the smaller frustules, one of 

 which is less in size than the other (fig. 21). These, after ap- 

 proximation (fig. 22), become invested in mucus, and, presently, 

 exhibit their endochromes in two globular masses between them 

 (fig. 23) ; elongation of the sporangial frustules which enclose 

 these respectively takes place, transversely to the long diameter 

 of the conjugating frustules (fig. 24) ; the former then assume a 

 bent form towards each other, and the endochromes becoming 

 irregularly scattered through them, they attain their utmost de- 

 velopment (figs. 24-27). Meanwhile the valves of the conju- 

 gating frustules become separated, and two remain at the ends 

 of the sporangial frustules, while the other two appear about their 

 middle, one on each side (fig. 27). The mucus then becoming 

 dissolved, the valves of the conjugating frustules are thrown off, 

 and the sporangial frustules are thus set free. The large con- 

 jugating frustule bears to the sporangial frustule (fig. 28) the 

 proportion of jj^^ to ^^^j of an inch ; at least, these are their 

 respective measurements. 



Observations. — Nothing can be more obvious in these pro- 

 cesses, than that one point gained by the conjugating of the 



1* 



