BY R. VON LENDENFELD, PH.D. 315 



HiSOTOLGY. 



Although our sponge does not present any interesting peculiarities 

 in most respects, it is still remarkable for the development of its 

 nervous system. 



I have found that the surrounding of the horny fibres near the 

 tips of the conuli are very similar to those described by me of the 

 Australian Aplysillidaj (1). As in those we find (Plate XXX., fig. 

 18) a coating of Spongoblasts around the growing fibre (aS*). These 

 are very small, measuring only 0-006 mm., in length, they are three 

 times as high as broad. In the distal, rounded end we find a very 

 elongate nucleus. Outside, this layer of Spongoblasts is covered by 

 a layer of spindle-shaped longitudinal tissue cells (5). Here and 

 there we find a thread formed of similar cells {B') extending 

 through the soft part of the sponge and joining the hollow cylinder 

 foi'med by those tissue cells which cloth the horny fibre. 



The horn fibre is clearly striated {H) and a granular axial canal 

 {A) can be detected. 



The Nervous System. 



(Plate XXXIV., fig 23.) 



The reader will remember, that elements of calcareotts sponges (2), 

 have been described by me as being nervous cells. In Aulena 

 similar elements have been found by me, which I consider to have 

 a nervous function. 



At the joining lines of the membranes which pervade the vestibule 

 space, where the membranes are thickened, numerous spindle- 

 shaped cells are found in groups. These are immersed in the 

 ground substance and vertical to the sui-face. 



They are 0-01 mm. long, and in the middle 0-002 mm. thick. 

 The distal end is protracted to form a short hair or cilia, a Palpocil 



(1) R. V. Lendenfdd. Ueber Coelenteraten der Siiclsee, II. Mittheihmg 

 Neue Aplysinidse Zeitschrif t f iir wissenschaf tliche Zoologie. Band XXXVIII. 



(2,1 R. V. LencUnfeld. The Histology and Ners-ous system of Calcareous 

 Sponges. Proceedings of the Linnean Society. Vol. IX. 



