60 E. LÖNNBERG, ON THE CEPHALOPODS. 



I have already mentioned tliat some of the above described 

 tissues resemble those of tbe »terminal papilla» of Spirula 

 reticulata, and in describing this organ I ventnred to guess 

 that it migbt bave »the function of belping the animal to 

 apprehend the hydrostatic pressure». The probability of this 

 hypothesis seems strengthened by the above related facts. 

 Both Spirula and Onychoteuthis ingens descend to great depths 

 in the ocean and thus need an organ of this kind as it might 

 be fatal for both to ascend above a certain limit. In both 

 oases is the analogy of structure apparent. We find a body 

 limited from the surrounding tissue by a dense Stratum of 

 fibrous structure — the lenticular body with its capsule of 

 Spirula and the papilhe of Onyclioteuthis ingens with their 

 Stratum limitans — both are furnished witb nerves and 

 bloodvessels and are surrounded or imbedded in a soft tissue. 

 In both animals these papillre rise from a comparatively firm 

 base whereby their function of apprehending the pressure is 

 made easier. This firm base is in the former animal the 

 shell, in the latter, the compact pallial musculature. The 

 difference is that Spirula only has one such organ but 

 Onychoteuthis a great number and that, in the latter case, 

 the papillse and the surrounding tissue form not only an organ 

 of apprehension, but also may have other functions. 



An outer layer of soft tissue is known from several 

 Cephalopods with benthopelagic habits, although its structure 

 has not been studied. In Mastigoteuthis levimana Lönnb. 

 there is a rather thick glassylooking subcutaneous layer, 

 but there does not seem to be any papilhe like these of 

 Onychoteuthis ingens. In Älloposus mollis Verrill this soft 

 layer according to Joubin 1 consists of a gelatinous tissue 

 with elastic fibrils. But in this form there is said to be 

 radially (vertically) disposed muscles, too, which probably 

 have some regulating function. Although not exactly similar, 

 these conditions show some analogy with the above described 

 facts. But the late Prof. Steenstrup has with his keen eye 

 observed some features of structure in several species of 

 Ommatostrephes before all 0. pteropus Stp. and 0. gi'jas d'ÜRB. 

 which by a new investigation may prove identical with these. 

 In the paper entitled »Professor A. E. Verrills to nye 



1 Ref. by Appellöp: Zool. Centralbl. TU 1896 p. 175. 



