228 Miscellaneous. 



injection, so that I believe (as may be verified in spirit specimens) 

 that in the Pleurobranchus the circulatory apparatus communicates 

 directly with the exterior. 



The demonstration of a direct communication between the exterior 

 and the circulatory apparatus, renders the assumed existence of an 

 aquiferous system a priori less necessary, in order to explain the 

 great changes of volume of the body of Mollusks. But I believe 

 that, in addition, microscopic examination will show the direct con- 

 tinuity of the genital glands with the lateral orifices placed at the 

 base of the foot in the Lamellibranchiata. 



This communication of the vascular apparatus with the external 

 water, has a very important bearing on the history of the nutritive 

 processes. The physiological conceptions derived from the study 

 of the higher animals are singularly affected by finding creatures 

 which can at will throw out a portion of their blood, or, on the 

 contrary, dilute with water that which is, par excellence, the nutri- 

 tious element. 



This would be sufficient to prove, were it necessary to do so, how 

 wide is the difference between the vital processes of the lower and of 

 the higher animals. 



MISCELLANEOUS. 



On the Hydra rubra of Mr. Lewes. 

 By the Rev. W. HOUGHTON, M.A., F.L.S. 



To the Editors of the Annals of Natural History. 



Solihull, Feb. 10, 1860. 



GENTLEMEN, In your January Number, Mr. G. H. Lewes 

 records the discovery, on Wimbledon Common, of what he terms a 

 new species of Hydra. His description of the animal is, that it is 

 "a beautiful bright-red species, differing in intensity of colour in 

 different states of the animal, being sometimes of a brick-dust hue." 

 Van der Hoeven, Mr. Lewes says, enumerates three species of Hydra, 

 which he calls H. viridis, H. fusca, and H. grisea respectively. 

 Now, the authors of the ' Micrographic Dictionary ' mention four 

 species, namely, H. viridis, H. fusca, H. attenuata, and H. vulgaris. 

 Dr. Landsborough, also, in his little book, ' The History of British 

 Zoophytes,' describes these same four species, with the addition of 

 Hydra oligactis (Baker). The description Dr. Landsborough gives 

 of H. vulgaris (for it is to this species I wish to direct attention) is 

 that it is about the same size as H. viridis, but that it differs from 

 it in colour, " being of an orange-colour, or sometimes of a brown, 

 or even red tint." Under the word " Hydra," in the ' Micrographic 

 Dictionary,' I read the following description of H. vulgaris : " Body 

 orange-brown, yellowish, or red." How does this differ from Mr. 

 Lewes' s so-called new species? 



Why this animal has ever been designated as //. vulgaris I am 

 at a loss to conceive. I have searched pools and ditches innumer- 

 able for Hydra ; and my experience tends to show that this species 



