104 Miscellaneous. 



communication with the ambient liquids by exeeediugly delicate 

 canals starting from their periphery, a certain number of which 

 open at the surface of the perforated shells. On this hypothesis 

 these canals would represent the afferent apertures of the Cliono'. 



In thin plates of shells the perforations of the Dendrma' are seen 

 to be composed of more or less numerous irregularly branched 

 vacuoles, which are inflated here and there, but retain throughout a 

 pretty wide diameter. The youngest are ovoid or lageniform. 



Although the size of the Dtndrina' is variable, it is rare for an 

 individual from the French coast (Dendrina europo'a, Fisch.) to 

 attain 0'8 millim. ; generally the maximum diameter is 0-6-0-7 

 millim. The large osculum measures 0-07 millim., and the lobules 

 vary between 0-OG and 0-U8 millim. in diameter. I have counted 

 from 60 to 80 individuals of Dendrhia upon a surface of 1 square 

 centimetre of the shell of Pecten opercularis. 



When a Dendrina is highly magnified, a quantity of minute canals 

 are seen to start from the periphery of the lobules and penetrate the 

 perforated shell in all directions. These canaliculi are cylindrical, 

 rectilinear, slightly dilated near their point of emergence, truncated 

 at their extremities. Sometimes some are a little wider than the 

 others, or slightly curved. Each canaliculus seems to have a distinct 

 origin ; there are no anastomoses or bifurcations ; the interior is 

 filled with a brownish organic material. Their length is from 0-()3 

 to 0-06 millim., and their diameter from 0-0010 to 0*0015 millim. 

 It may he supposed that sarcodic processes more or less analogous 

 to the pseudopodia of the Khizopods pass into these canaliculi. 



I have been unable to ascertain the existence of spicules in the 

 interior of the Dcndrince, even with a power of 500 diameters. We 

 see no trace of the siliceous plates or corpuscles which consolidate 

 the surface of the Clionce and lUiooscp. 



The Dendrincv. cannot be confounded with young Clionre. The 

 latter have a more or less rounded initial chamber of much larger 

 dimensions ; in a more advanced stage the excavations of the CUonce 

 are united to each other by narrow canaliculi, and several oscula 

 open at the surface of the perforated body, whilst in the Dendnnce 

 there exists only one principal orifice, at which the canal penetrating 

 into all the lobules terminates. 



The size of the Cliona' is only limited by the extent of the per- 

 forated body ; sometimes, even, the Clionre, which have commenced 

 their work of destruction at various points, become confounded into 

 a mass by a process to which I have given the name of aggregation 

 hi co(di>scenc<'. The dimensions of the Dendnnce arc comparatively 

 limited, and hardly vary more than those of the existing Foramini- 

 fera. This last character, with the presence of the peripheral cana- 

 liculi and the absence of spicules, leads me to regard the Dendr'mcp 

 as a peculiar type of perforant Barcodaria more nearly related to the 

 Rhizopods than to the Sponges. — Compfes Rcndus, December 6, 

 1875, p. 1131. 



