Miscellaneous. 443 



blood, but of four times their diameter, and formed of a proteic 

 substance, the ready alteration of which induces a rapid deformation 

 of these corpuscles ; (2) granular spherules furnished with singular 

 processes, which, by interlacing, often agglomerate these bodies 

 into masses of variable size : these bodies, which I propose to call 

 villous globules, occur also in the cavitary liquid of many Inverte- 

 brata, and have been mistaken for portions of vibratile tissue. The 

 vessel, forming a simple or double caecum, which is attached to the 

 first portion of the digestive tube and opens into the tentacular 

 crown without furnishing ramifications to the integuments, contains 

 discoid corpuscles very similar to those of the cavitary liquid, but of 

 rather larger diameter. The corpuscles are set in motion by a 

 ciliary epithelium, which likewise lines the interior of the tentacular 

 crown. This tube, in my opinion, represents a very rudimentary 

 circulatory system : whenever a portion of the nutritive fluid is 

 vascularized, this vascularization is generally for the benefit of the 

 function of respiration. The delicate structure of the tentacular 

 membrane, and its relations to the vessel which I have just described, 

 lead me to think that, as asserted by Dr. Williams, this region is the 

 principal seat of hsematosis. The thicker integuments, in contact 

 only with the mud or muddy sand in which the Sipunculus lives 

 enclosed, only play a secondary part, but, nevertheless, one which we 

 cannot deny. The cavitary hquid, in fact, is subjected to a double 

 movement of transport, perfectly recognized and described by M. 

 Quatrefages. This movement is caused by vibratile cilia distributed 

 over the surface of the digestive canal ; and the fraena here and 

 there bind together its convolutions : the inner wall of the tegumen- 

 tary envelope is destitute of these appendages. 



With regard to the caecal tubes, in which certain anatomists have 

 been inclined to recognize an organ of respiration, the following is 

 the view which seems to be most plausible. They are formed 

 essentially of a structureless membrane, strengthened by some 

 smooth muscular fibres forming an irregular network, and by a 

 layer of cells with brownish granular contents, such as occur in the 

 gland destined, in many Invertebrata, to eliminate uric acid. The 

 product of secretion, in the form of a clear greenish-brown liquid, 

 often distends these caeca, which I regard as an organ of elimination 

 analogous to the gland of Bojanus. These organs also serve for the 

 emission of the ova and sperm atozoids — a purpose which we also 

 sometimes see fulfilled by the organ of Bojanus. 



I was unable to make out with certainty where and how the ova 

 and spermatozoids are formed. I did not succeed in detecting the 

 generative organ, the development of which is perhaps temporary. 

 I have, however, sometimes seen, on the terminal portion of the in- 

 testine, pedunculated vesicles, which might perhaps be very young 

 ovigenous or spermatogenous cells. The question is still too obscure 

 to allow me to hazard an assertion ; and I propose to resume it by 

 studying the nearly unknown embryology of these Gephyrea. — 

 Cotnptes Rendus, April 29, 18G7, pp. 8/1-8/3. 



82* 



