424 Prof. Ehrcnberg on Hyaloiiema lusitanicum, and 



It has always struck me as very remarkable that in the many 

 investigations of the largest and smallest forms of life which I 

 have carried on under multifarious and favourable conditions, I 

 have never met with an animal with a constantly open mouth and 

 digestive cavity; whilst in the Sponges, both of the sea and of 

 fresh water, I could find nothing but constantly open tubes, 

 which never closed even periodically or under the influence of 

 n-ritation. Nay, I have always found a physiological impossi- 

 bility in the notion that a tube with no obstacle to the access and 

 change of water, even when clothed with a ciliary coat, can fur- 

 nish any assistance to zoochemical assimilation or digestion. 

 Decomposable matters may certainly become putrid and soluble 

 in water in them, and be thrown out again ; but a constant change 

 of water will not bring even this to assimilation. On the other 

 hand, the periodically and voluntarily closable mouth of animals 

 is usually aided by a second closure, which is to be characterized 

 as the oesophagus, and is retained by nature in a very remarkable 

 manner even down to the smallest forms of animals, by which 

 means the quiet segregation of the materials conveyed into the 

 interior of the body for assimilation is greatly favoured. The 

 observations so carefully made since the year 1856 by Lieberklihn 

 and Wagner upon the organization and reproduction of the 

 SpongillcE certainly furnish many characters which seem to 

 be in favour of their animal nature; and these have also 

 quite recently been recognized by Van Beneden*, as also by 

 Hackel, as animal characters. But the great irregularity of this 

 organism, which is also frequently formed by the fusion of several 

 individuals, and the slight filling of its so-called nutritive cells 

 with recognizable materials even during very rapid growth, appear 

 to me to have not yet admitted a satisfactory solution of the 

 mystery. It is true the large open tubes of the Spongillce are the 

 more shown not to be polype-bodies ; but the essential charac- 

 ter of all animals known to me is remarkably wanting — namely, 

 the individual separation of a single organism, which constantly 

 occurs in animals, and is as constantly wanting in plants. I 

 have never been able to obtain accumulations of indigo or carmine 

 in SpongillcB and sponges, either in tubes or in round cells, in the 

 way so distinctly presented by even the smallest of true animals; 

 and the deposits of indigo noticed by the above-mentioned ob- 

 servers are clearly not regular aggregations, and are only so 

 represented even by them. I must here not allow the fact to 

 pass unnoticed that I always expect to find cesophagoid contrac- 

 tile organs behind the mouth in all animals : these, in the Poly- 



* Recherches sur la Faune littorale de Belgiqiie, Polypes, IBGC, (Mem. 

 Acad. Belg. tome xxxvi.) p. 198. 



