28 jMr. A. H. Hassall on the Anatomy and Physiology/ 



' Flora' : — " In Z. elongatum, Ag., the dissepiments have a very 

 pecuhar structure^ which I have found in no other species. The 

 terminal sm-facc of each cell is not even, but elongated into a blunt 

 conical process. This process can only be observed in its true 

 state when two joints are separated one from the other ; when, on 

 the contrary, the threads are unbroken the process is generally 

 introverted like the finger of a glove, and exliibits the form repre- 

 sented at PI. I. tig. 8. a, b, c. This is the common condition, and 

 in most threads no joint is found otherwise constructed. But I 

 have now met with a single thread in which a part of the articu- 

 lations have the ordinary length, while another part has joints 

 only half as long. In these shorter articulations it was normal 

 that only the alternate dissepiments had the structm*e peculiar 

 to this species (so that by these dissepiments the thread was 

 divided into articulations of the ordinary" length), while, on the 

 contrary, the intermediate dissepiments exhibited the form usual 

 in Confervge*.^^ 



The observation, that " this process can only be observed in its 

 true state (that is, everted) when two joints are separated the one 

 from the other," is inaccm'ate, for the cells may be separated and 

 yet the processes inverted, the eversion of them having nothing 

 whatever to do with the separation of the cells, and never being 

 in any case the result of it, but depending, as explained already, 

 upon unequal internal pressure, and occmi-ing chiefly at the pe- 

 riod of reproduction. The effect of the eversion is, as already 

 observed, to occasion the dislocation of the cells. 



Again, in every filament of those Zygnemata which exliibit the in- 

 verted structm'e, cells may be observed terminating in the ordinary 

 manner of Confervte, viz. by plane surfaces, the presence or absence 

 of the inversion depending upon the period of the formation of 

 the dissepiments ; the older ones, or, as observed in the beginning 

 of this notice, the more mature ones only presenting it. Thus it 

 follows that the opposed ecctremities of cells always exhibit the same 

 structure, and that this alternation in form supplies e\ idence the 

 most conclusive of the multiplication of cells throughout the en- 

 tire filament of a Conferva by division. 



Observations on the genus Vesiculifera. 

 The genus of freshwater Confervse which I have denominated 

 in a pre\'ious article Vesiculifera, in addition to the characters 

 indicated in the definition of it given therein, such as the attach- 

 ment, attenuation and slight mucosity of the filaments of the spe- 

 cies composing it, as well as the formation of true spores by the 

 intermingling and union of the contents of two cells in the same 



* Flora, 1837, vol. i. p. 29. 



