" EINAR LÖNNBERG: NOTES ON SPIRULA RETICULAl 





and that the male also possesses a similar apparatus. Pelsend ,l„ - th, struc- 



ture of the "aboral fossa" of Spirula peronii and supposes that the papilla may be 

 a "protective prominence"; this opinion seems to him confirmed by th that 



the "terminal papilla has precisely the situation of an orgai tectbo for the 



aboral extremity". And he adds "in the majority apods tl 



copied by the point of the rostrum". It is true that when a rostrui it it 



is situated at the aboral end of the body, but the physiological end 

 not homologous in all Cephalopods. Owing to the ventral curvation of the shell 

 and of the soft parts of Spirula, its hind-end and the situation of the "terminal 

 pilla" correspond to a place on the dorsal face of most other Cephalq 1 his 



can be easily perceived from the situation of the terminal papilla as compared with 

 that of the lins (see above). The rostrum of other Cephalopods has m 

 quite a different origin, since it is formed in the shell sac, as Pelseneer points out. 

 Thus, even if the "terminal papilla" were a protective prominence, which I do not 

 believe, it is not at all homologous to the rostrum of other Cephalopo» it is 



quite free and separated from the shell. It is clear that during the ontogenetic 

 development of the latter and its rolling up in an "endogastric" direction, 

 part of the shell in time gradually changes its position from a dorsal to a terminal, 

 and from that to a ventral one and so on. Spirula could not therefore possibly 

 have a rostrum in the same sense as other Cephalopods, for in them the terminal 

 point of the body, at least after a certain age, is quite fixed 1 . 



Our specimen of Spirula reticulata is not in a perfect enough condition t<> 

 allow the finest histological details to be studied, but I have made some sections ol a 

 small part of the "aboral fossa" and the "terminal papilla", and am thus able to give 

 a sketch of the structure of these organs, which seems different in some parts from 

 that of Spirula peronii described by Pelseneer. The lips round the circular aperture 

 to the inner cavity of the "aboral fossa" are rather stiff and elastic. This consistency 

 is attributable to an internal lamella of "hemichondroid" tissue. This hemichondroid 

 lamella is clearly defined from the surrounding connective tissue, being much n 

 darkly stained. This is because its firm intercellular substance imbibes and retains 

 the hematoxylin more readily. The large cellules are situated in ellipsoidal holes 

 in the intercellular substance, sometimes two in the same hole. These hoi 

 nected with each other by canals-', which probably form an irregular network through 



1 Even in Spirulirostra which as regards the shell is must similar to Spirula the rostrum ( 

 seem to be developed before this terminal end has been fixed, to judge, at least, by th 

 structure of Spirulirostra. 



'-' The cellules of the true cartilage of the cephalopods (e. g. Stpioteuthii) have als. 

 tic and ramified pro« esses whereby they are brought in connection with each other t 



