544 



JOTTINGS FROM THE BIOLOGICAL LABORATORY OF 

 SYDNEY UNIVERSITY. 



By Prof. William A. Haswell, M.A., D.Sc. 



No. 18 — Note on Certain Points in the Arrangement and 

 Structure of the Tentaculiferous Lobes in Nautilus 

 po?npil{us. 



(Plate XLViii.) 



In writing a short account of the structure of Nautilus for a 

 general work I have had occasion to examine a considerable 

 number of specimens, and in doing so have noticed one or two 

 points to which attention has, I think, not hitherto been directed. 

 The most important of these, with which alone the present com- 

 munication deals, has to do with the tentaculiferous lobes of the 

 foot, and their sexual modifications. 



No fewer than three papers published or read recently deal 

 with sexual differences in Nautilus. Two of these, one by 

 Willey,"^ the other by Vayssiere,t refer only to sexual differences 

 in the shell ; the third, by J. Graham Kerr, | is referred to below. 



The tentacles of Nautilus are arranged in two series — an outer, 

 and an inner. With the outer series we are not at present 

 concerned. The inner series exhibit a marked sexual difference in 

 their arrangement. In the female this inner series consists of 

 two symmetrical lateral lobes, each bearing twelve tentacles, and 

 of a median (posterior) portion. In the male the two lateral 

 lobes of the inner series are unsymmetrically developed, four of 

 the tentacles of one side, usually the left, being modified to form 

 the structure known as the spadix. 



The spadix was first described by Van der Hoeven.§ He 

 calls it "a great conoid body, the length of which was nearly 2^ 



* Natural Science, June, 1895. 

 t Comptes Rendus, 24th June, 1895. 

 + Zoological Society of London, Abstract of Proceedings, June 18, 1895. 



§ Trans. Zool. Soc, Vol. iv., p 27. The earlier Dutch papers are not 

 accessible to me. 



