422 Prof. Ehrenberg on Hyalonema lusitanicum, and 



and very meritorious German systematic student of sponges has 

 adopted the opinion of those who regard the marine sponges as 

 animals ; and the beautiful observations upon the motile young of 

 the Spongillce, as well as the demonstrated filling of many tubes in 

 the horny sponges with fine sea-sand^ in which there are Poly- 

 thalamia and Bacillaria, appear to many naturalists to be suffi- 

 cient proofs that the reception of solid nutriment into the interior 

 of the body of these organisms really takes place. The cilia and 

 fine motile filaments observed here and there upon sponges 

 strengthen these arguments. But neither the ciliary organs, 

 which also occur on the swarm-spores of plants, nor the tubes, 

 nor the anti-vital (lebenswidrige) filling of the tubes of many 

 horny sponges with sand, evidently after their death, appear to 

 me sufficient to prove the animal organization of these objects. 



Hitherto we have no observation of the primary character of 

 all true animals, the limitation of an individual, which is unmis- 

 takeable in all true polypes, and is distinct even where the indivi- 

 dual forms are intermixed and coalescent below^ as in the Ascidia 

 composita, Se7iuIarince,Halcyonell(S,SindmsL\iy similsiv forms. Sepa- 

 rate individuality, the reception of solid nutriment through a mouth 

 into internal spaces, very different from tube-currents through 

 cellular tissues, as also frequently quite distinct muscular sub- 

 stance for contractions, very different from contractile tissues, as 

 demonstrated by me and others in Vorticellince, Stentorince (con- 

 firmed in 1857 by Lieberkiihn), Cmxhesium, Operculmia, and 

 most strikingly in the Rotatoria and many similar animals, are 

 characters still undetected in sponges, and which separate ani- 

 mals from plants. Nay, in microscopic animals, as so distinctly 

 in the Crustacean Cj/clopida and many others, the eye-spots may 

 not unfrequently directly indicate a nervous system, the colour- 

 less transparency of which may often cause it to appear to be 

 wanting. Even in Ophryoglena flavicans a confirmatory greater 

 complication was indicated by Dr. Wagner in 1856. Un- 

 doubtedly it must be pointed out that the most recent and best 

 observers constantly discover new conditions of organization — 

 ^. e. greater compositeness, which is quite in opposition to the 

 notion of unicellularity, but not suited to disprove animal 

 organization. 



In the elucidation of the question whether the Sponges may be 

 regarded as polypoid animals of a low grade of organization, 

 which have been named sometimes Protozoa, sometimes Zoidia, 

 sometimes Amorphozoa, and so forth, we must not pass over the 

 fact that of late there has seemed to be more to justify our re- 

 garding the bodies lying in the interior of these structures near 

 the base as ova, especially as their development into perfect 

 swarming young has been carefully traced, and even spermatozoid- 



