116 MEMORANDA. 
interest of the phenomenon being enhanced by the cireum- 
stance of its occurring in the tail of a larval Trematode— 
Cercaria macrocerca of Filippi. I do not find any explana- 
tion of this structure in the essay itself, nor in Wagener’s 
more recent ‘ Helminthologische Bemerkungen,’ published 
in the same number of Siebold and Kolliker’s ‘ Zeitschrift,’ as 
that in which Claparéde’s memoir is contained.* In Professor 
Van Beneden’s ‘ Vers Cestoides’ mention is made of these 
tubular extensions, in the detailed and accurate description of 
this Cestode there given; and I have not yet received (De- 
cember Ist) his great Prize volume—only a few copies having 
at present crossed the Channel. 
Although I have elsewhere expressed my adhesion to the 
views of Siebold and others as to the dermo-skelctal cha- 
racter of the calcareous bodies, I suppose we must—if Clapa- 
réde’s observations are correct—henceforth regard these flask- 
shaped capsules, with their contained sclerous particles, as 
excretory organs, notwithstanding that they do not appear to 
have any connexion with the water-vascular system. 
Note on a Structure observed in Surirella—In the course of a 
recent examination of some slides of Californian guano, the 
material of which was communicated to me by Mr. J. T. 
Norman, I observed an example of a species of Surirella, 
exhibiting an appearance of considerable interest. The 
frustule (which presents the side view) is injured, a consider- 
able portion of the valve nearest to the eye being removed ; 
the result is the exposure of a structure which, so far as I 

Length -0040”. Breadth :0019”. 
001”. Strie of median line 25 in 001”. 
know, has not hitherto been noticed. This structure is a 
strong, areolated septum or valve of a yellowish colour, 
stretching across the entire frustule, distinct from, and 
* See Translation, in another part of the present number of this 
Journal, 
