162 Mr. H. J. Carter on the Conjugations of 



which three bog-species, viz. Navicula serians, N. rhomboides, 

 and Pinnularia gibba appeared in different stages of conjugation, 

 each presenting the ribbed sheath above mentioned. They were 

 enveloped in a gelatinous substance which is so common and so 

 remarkable in the heath-bogs about the neighbourhood of Bud- 

 leigh Salterton, that it seems worthy of a short description. 



This jelly-like mass, which is colourless or whitish so long as 

 it is not permeated by green Algse, covers the surface of the 

 water in the depressions of the bogs, in a sheet-like form, about 

 half an inch or more in thickness, fragile and of a granular 

 consistence, while the number of living and dead frustules of 

 Diatomese in it, frequently to the almost total exclusion of all 

 other organisms, seems to indicate that for the most part, if not 

 entirely, it is produced by the Diatomeas themselves. 



Be this as it may, it was in a portion of such jelly (where I 

 had expected to find them, and where I hope to find more), re- 

 posing on gravel through which a spring was oozing, that I 

 observed the three species mentioned in profuse conjugation 

 respectively, and in all stages; but as Navicula serians afforded 

 the best typical examples, I shall, in accordance with my 

 delineations, describe it first and most particularly. 



Before entering upon the description, however, I would pre- 

 mise that all the figures in the plate, with most of their detail, 

 are drawn upon the scale of -jMh to -g^Voth of an inch, and the 

 arrangement of their elements just as they appeared under the 

 microscope, with the exception only of fig. 1. (PI. IV.), in which 

 the spore-cell (c) was not visible, and the conjugating frustules 

 were so much separated from their contents by the necessary 

 pressure of the covering-slide on the jelly in which they were 

 imbedded, to bring them into focus, that, to replace the former 

 and to restore the latter to a position in which they might be 

 seen, the whole has been delineated as represented in the figure. 

 Hence some little doubt exists in my mind as to whether the 

 process commences with one, or directly in two spore-cells (as in 

 fig. 2) ; but for the present I shall describe it as commencing 

 with the former. 



Thus the reader will be able to obtain a just idea of the rela- 

 tive size and position of the different conjugations and their 

 elementary parts, as well as their actual dimensions by measure- 

 ment. The dark shade represents the endochrome, and the 

 circles the oil-globules, characteristic of the confused mass which 

 the whole forms when forced into the spore. 



It is true that these elements are more or less distorted by the 

 pressure to which I have alluded; but this is more than counter- 

 balanced by their being so far kept together by the jelly in 

 which they are imbedded, that the observer neither loses any of 



