KOLLIKER, ON VEGETABLE PARASITES. 173 



know, only by Quekett, I myself at first regarded these as a 

 peculiar plasmatic canal-system, and congratulated myself 

 upon being able to add something to the knowledge of the 

 organization of this skeleton, until further investigation 

 taught me better. 



From Dr. Bowerbank I have received sponges infested 

 with fungi, with the statement that these sponges exhibited 

 a special tubular system. As regards Rose and Claparede, 

 these authors, although they conjecture the foreign nature 

 of the tubes in fish-scales and shells of Neritina, were not 

 in a position to express any definite opinion regarding their 

 nature and origin. If to this it be added, that systems 

 of tubuli, whose nature is not so easily explained, are met 

 with in several other tissues besides those already men- 

 tioned, as in the chitinous structures of the Articulata, 

 in the axis of Virgularia, in the hard tissues of the Echino- 

 dermata, the scales and bones of living Ganoid fishes, it is ob- 

 vious that a careful comparison and investigation of these con- 

 ditions is an indispensable and important zoological problem.* 



With these preliminary remarks, I will now proceed to 

 give an account of the special observations I have made. 



1. Sponges. 



During my last stay in England, in the spring of 1859, 

 I obtained, through the kindness of Dr. Bowerbank, a 

 series of sponges, amongst which were two having tubular 

 structures in a horny skeleton. The more marked one 

 of these was described by Dr. Bowerbank as a " sponge 

 from Australia, nearly allied to the fossil genus Choanites ;" 

 and he added, that " it presented a peculiar form of horny 

 skeleton, whose fibres are covered with a network of tubules." 

 The close investigation of this sponge afforded the following 

 results. 



The skeleton of the sponge itself, to judge from the small 

 fragment at my disposal, was wholly composed of a network 

 of the well-known yellowish, horny fibres, as they are 

 termed, which presented no peculiarity, except that the 

 fibres were of very various dimensions. Whilst the smaller 



* Since the above was -written, I have received a work by Weld, " On 

 the Nature of the Canals which exist in the Shells of several Acephala and 

 Gasteropoda," contained in the * Sitz. bericht. d. Wien. Akad.,' Bd. xxxiii, 

 p. 451, 1859. Wedl communicated his observations to the Academy on 

 the 14th October, 1858, and they consequently have precedence of mine; 

 but as they refer only to two divisions of the lower animals, I still regard 

 the publication of my research.es as not superfluous, and the more so because, 

 in the explanation of the nature of the parasites, I am not wholly in 

 accord with Wedl. 



VOL. VIII. P 



