2 Mr. H.J. Carter on the Conjugation of 



harenSy vulgare and neglectum ; and lastly in Dickieia Danseii *. 

 Since that, no one seems to have added any more instances of 

 this process of reproduction in the Diatomese, until Dr. J. W. 

 Griffith noticed it in a species of " Navicula f j" and lately I 

 have seen it in Cocconeis Pediculus (Kg.), Cymbella Pediculus 

 (Kg.), and Amphora ovalis (Kg.), mihi, under such circumstances 

 as to enable me to offer the following descriptions and figures 

 of it respectively, in each of these genera. 



Cocconeis Pediculus (Kg.). On the 4th of September, I per- 

 ceived a brown incrustation extending over the sides of a basin 

 in which Nitella, infested with Fragilaria and Cocconeis, had 

 been kept for upwards of three months; and on examination 

 with the microscope, it proved to be the latter, of different sizes, 

 undergoing conjugation and deduplication. 



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

 which is less in size than the other (PI. I. fig. 1). These, after 

 having become approximated, secrete a mucus which holds 

 them together, while the lining mucus-membranes or primordial 

 utricles respectively burst open the valves of their frustules 

 (fig. 2), and approaching each other unite to form the spore 

 (fig. 3) ; the latter then assumes a spherical form and the endo- 

 chromes become mixed (fig. 4), after which the spherical form 

 becomes elongated and finally elliptical (fig. 6) ; when, the endo- 

 chrome also becoming scattered in more or less detached por- 

 tions over the circumference, a single line appears, dividing the 

 spore longitudinally into two somewhat unequal parts (fig. 7) ; 

 two other lines then present themselves, one on each side the 

 first (fig. 8) ; and the latter, passing into a groove, soon effects 

 a deduplication of the spore, which then becomes divided into 

 tw^o sporangial frustules and thus the process is completed 

 (fig. 9). Very soon after the spore has become spherical, the 

 valves of the small conjugating frustule are thrown off, so that 

 it is only now and then that they are seen ; while the valves of 

 the large one remain attached to it until deduplication com- 

 mences. The large conjugating frustule bears to the sporangial 

 frustule (fig. 11) the proportion of yy^y to jjj of an inch ; at 

 least these are their respective measurements. 



Cymbella Pediculus (Kg.). On the 17th of August, after 

 having had a matted portion of Cladophora, Spirogyra and Oscil- 

 latoria together in a basin for a few days, a number of Cymbellce 

 of different sizes left the filaments and came to the sides of the 

 vessel, where they conjugated. 



* Ann. and Mag. Nat. Hist. vol. i. p. 161. pis. 11 & 12, 1848. 

 t Ideniy vol. xvi. p. 92. August 1855. 



