92 Dr. J. W. Griffith on the Conjugation of the Diatomacese. 



EXPLANATION OF PLATE V. 



[The figures represent the specimens magnified 4 diameters, with the 

 exception of 16 b.\ 



Fig. 1 a. Beyrichia Buchiana, Jones : right valve. 1 b. Ventral aspect of 

 ' the same valve. 2. Left valve. 3. Left valve of old specimen. 



Fi(/. 4. Beyrichia tuberculata, Kloden, sp. : right valve (young individual). 

 5 a. Right valve. 5 b. Ventral aspect of the same valve. 6. Left 

 valve. 7 «• Left valve (old individual). 7 b. Ventral aspect of 

 the same valve. 8«. Right valve. Sb. Transverse section of 

 the right valve. 9 a. Left valve. 9 b. Ventral asjject of the same 

 valve. 



Fig. 10 a. B. tuberculata, var. nuda, Jones : right valve. 10 b. Ventral 

 aspect of the same valve. 11. Left valve. 



Fig. 12. B. tuberculata, var. antiquata, Jones : left valve. 



Fig. 13 a. Beyrichia Dalmaniana, Jones : right valve. 13 b. Ventral 

 aspect of the same valve. 



Fig. 14. Beyrichia Maccoyiana, Jones : right valve. 



Fig. 15 a. Beyrichia Salteriana, Jones : right valve. 15 b. Ventral aspect 

 of the same valve. 16 a. Left valve. 16 6. Highly magnified 

 view of part of the border. 



Fig. 17. Beyrichia Wilckensiana, Jones : Left valve. 18 a. Right valve. 

 18 6. Ventral aspect of the same valve. 



Fig. 19. B. Wilckensiana, var. plicata, Jones : right valve of large indi- 

 vidual. 20 a. Right valve. 20 b. Ventral aspect of the same 

 valve. 21. Left valve. 



Fig. 22. Beyrichia siliqua, Jones : right valve. 



Fig. 23. Beyrichia mundula, Jones : left valve. 



VII. — On the Conjugation of the Diatomace^. 

 By J. W. Griffith, M.D., E.L.S. 



[With a Plate.] 



The interest attached to the conjugation and the relation of 

 the forms to the species of Diatomacese, will, I trust, render the 

 following remarks of interest to the botanist. 



At the end of May of the present year, I was fortunate enough 

 to find the bodies delineated in PI. II. B. figs. 1-5, in a ditch 

 near Blackwall. 



The first which attracted my notice was that represented by 

 fig. 3, and which could not be referred to any known Diato- 

 macean ; it was composed of silex, i. e. indestructible by heat 

 and nitric acid. Upon further search, other of these bodies 

 were found (fig. 2) containing a frustule of a Navicula, some 

 also with the valves of another Navicula (figs. 1 & 2) adherent 

 to the former. It was then evident that these bodies represented 



