132 A MONOGRAPH OF THE AUSTRALIAN SPONGES, 



work (50) appeared two years later. Kollikers observations 

 on the Histology of the Sponges, can be considered as the foun- 

 dation of our present knowledge of that subject. He discovered 

 fibrous cells which he correctly considers as muscles. He pointed 

 out that the horny skeleton of many sponges, as well as the 

 calcareous and siliceous spicules are to be considered as productions 

 of gland cells, and grow by apposition, a statement which has 

 recently been proved by F. E. Schulze (51) and myself (52). He 

 observed in many cases a cuticle on the surface of the sponges in 

 continuity with, and of the same substance, as the horn fibres. 



The correctness of this observation was doubted by F. E. 

 Schulze (1. c.) I have been able (1. c.) to prove that Kolliker's 

 statements on this point are perfectly correct, because, as we shall 

 see hereafter, sponges attain such a cuticle, when sick ; and it is 

 highly probable that Kolliker had studied only sponges that had 

 not been treated with the modern refinements of histological 

 investigation. 



F. E. Schulze's statement that such a cuticle does not exist is 

 perfectly correct for the healthy living sponge, and for specimens 

 treated in such a manner that they are killed before they have 

 time to get sick. 



O. Schmidt (53) published in 1865 his first supplement to the 

 Adriatric Sponges, in which his views on the Histology are 

 expressed. They differ from those of Kolliker. 



Lieberkuhn (54) dwells on the anatomical structure of the 

 calcareous sponges. He described in 1865 the configuration of the 

 canal system very accurately. 



(50). A. von Kolliker. Icones Histologics, 1. Abtheilung Protozoen 

 Leipzig, 1869. 



(51). F. E. Schulze. Ueber den Bau und die Erttwichelung cler Spongien. 

 DieFamilii der Spongidae. Z f. w. Z. Band 32, Seite, 593. 



(52). R. von Lendenfeld. Ccelenteraten der Siidsee II., Neue. Aplysinidce. 

 Z. f. w. Z Band 38. Seite, 234. 



(53). 0. Schmidt. /. Supplement zu den Spongien des Adriatischen 

 Metres, 1864. 



(54). N, Lieberkuhn. Beitrage zur Anatomie der Kalkspongien. Midler's 

 Arc hi v., 1865, p. 732. 



