308 Miscellaneous. 



different from that which he had observed in the other species, but 

 bearing, like the others, very long threads. The urticant cells here 

 not only cover the internal surface of the efferent tubes ; they are 

 diffused throughout the whole sponge, with their numerous cells of 

 formation in all stages of development. It can be proved clearly by 

 the latter that the essential part of the urticant cell (that is to say, 

 the urticant organ) originates from the nucleus. The different in- 

 dividuals here do not present the same uniformity that is observed 

 in the preceding species ; they are seen to differ the one from the 

 other in the numerical proportion of the cells in course of formation 

 and those fully developed. In certain specimens we only find cells 

 in course of formation ; in others, as, for example, in the colourless 

 variety, we no longer find even those. 



M. Eimer remarks that, whilst Leuekart and Hackel think that it 

 is through the calcareous sponges that the change from sponges to 

 corals takes place, the discovery of the urticant cells reveals a 

 remarkable affinity between the siliceous sponges and the Ccelen- 

 terata. 



In addition to these details on the urticant organs, the author 

 communicates the results of his observations on the nourishment of 

 the sponges, which consists of little Crustacea, like that of certain 

 polypes, and on the existence in these animals of incontestable 

 zoosperms. This is not the first time the existence of zoosperms 

 in the sponges has been noticed. Some bodies of that nature 

 were found by Lieberkiihn in the Spongillce ; and other natura- 

 lists have indicated their existence in marine sponges. But several 

 of these observations were contested ; it was supposed that, in 

 certain cases at least, flagellated cells or Infusoria had been taken 

 for zoosperms. M. Eimer figures perfectly characteristic zoosperms 

 which he has observed in numerous gelatinous, siliceous, and cal- 

 careous sponges. Through the tissues will be found distributed 

 spherical or oval balls, the surface of which appears gTanulated. 

 A very strong magnifying-power shows us that these granules are 

 caused by myriads of heads of zoosperms, which have their tails 

 turned inward. When this ball has been broken, it may be seen 

 that the head of the zoosperm bears a weU-developed anterior 

 prolongation or beak (Schnabel), which is darker than the other 

 portions of the head. Except the greater length of this prolonga- 

 tion, the head has quite the same form as the zoosperms in man. 

 The tail is of extreme thinness ; and we can onl)'- perceive it with a 

 very powerful objective, such as the immersion No. 10 of Hartnack; 

 and even then it is impossible to follow it thi-oughout its length. 

 We can, however, see enough of it to convince us that in the fuU- 

 grown zoosperms it is of an exceptional length ; often we can count 

 150 IX. These zoosperms originate from cells with distinct nuclei ; and 

 M. Eimer believes he has noticed that the head is formed at the 

 expense of the nucleus, whilst the filament originates from the proto- 

 plasm. He has always found with these zoosperms numerous ova ; 

 and for these reasons he considers the sponges to be hermaphrodites. 



At the same time that M. Eimer was studying the sponges at 



