MOLLUSCA. 15 



A second hypothesis of the function of the terminal disc and appendages, present in the 

 individuals or species of Spirula, might explain them as organs of adhesion or anchorage 

 when the creature wished to be at rest, and to resist the fluctuation of the surrounding 

 element; and this view derives some support from a passage in Rumphius' 'D'Amboinische 

 Rariteit-Kamer,' p. 68 ; where, after pointing out the distinction of the shell of the Spirula 

 from that of the young Nautilus Pompilius, he says : " But, on the contrary, these little Post- 

 Horns (Spirulce) have in their first chamber a slimy (or molluscous) animal, which does 

 hang to the rocks by a thin and small (disc or) door, through which the creature in the first 

 gate goes, and sets itself fast to the rocks.'"' ' The passage is obscure, and some of the 

 details unintelligible to me ; but my experience of the accuracy of Rumphius in regard to the 

 Nautilus major, or Pearly Nautilus, gives me confidence in his having drawn his statement 

 from nature respecting the Spirula. His description and figure (pi. xx. n. 1) of the shell 

 admit of no doubt respecting the genus which he was describing. 



On the hypothesis of the terminal disc and appendages being a specific character, the 

 Spirula devoid of them and with the last whorls of the shell exposed behind, might be indicated 

 under the name of Spirula Peronii, and the second synonym of Lamarck be restricted to 

 such individuals. 



To M. de Blainville's description of the soft siphon of the Spirula, as a solid tendon by 

 which the retractor muscles of the mantle are inserted into the calcareous hollow siphon, and 

 in which tendon they are said to terminate after filling the last chamber of the shell, I can at 

 present only oppose the clearly recognisable fact that the soft or membranous siphon in 

 Sir E. Belcher's specimens of Spirula was hollow, — in fact, a tube. I have already mentioned 

 that it was continued from the hard siphon and last chamber of the shell through the semi- 

 circular aperture of the mantle (fig. 6, sh,fn) into the visceral cavity, where it was lost in the 

 remains of the membrane or capsule of the lacerated termination of the liver. On gently raising 

 the exposed portion of the siphon (s/i, fig. 6) with a needle, the soft siphon was withdrawn 

 without sensible resistance from the tube of the hard siphon : the portion so withdrawn must 

 have reached nearly to the innermost whorl. It exhibited a slight segmentation answering to 

 the successively sheathed parts of the calcareous siphon. Under a magnifying power of three 

 hundred linear dimensions, the dark contour of the central cavity could be traced from end 

 to end, the larger extremity withdrawn from the body shewed plainly the circumference of the 

 aperture of the central cavity from which a minute filament, either vessel or nerve, protruded ; 

 the texture of the walls of the canal was minutely fibrous, the fibres being longitudinal, and 

 of the size of the elementary fibres of cellular tissue. This difference from the account of 

 the membranous siphon given by M. de Blainville 2 leads me much to desire the opportunity 



1 " Daar en tegen deze Posthoorentjes hebben in hunne voorste kamer een slymerig dier, tVelk aan de klippen 

 hangt, met eenen dunnen en smallen dooren, die door het beest en de eerste gaatjes gaat, en aan de klippen vast 

 zit," p. 68. The marginal indication of this paragraph is " En zit aan de klippen," i. e. " It sits on the rocks." 



2 " Le siphon de la coquUle est forme d'une suite de petits entonnoirs s'emboitant plus ou moins les uns dans 



