80 mOller on the male of 



lopoda, and indeed, as KoUiker observes, only upon females with 

 ripe ova. I have myself found the free Hectocotylus Argonautcs 

 only upon the inner surface of the shell, or upon the ova, or 

 fixed or creeping upon the animal itself, and I can affirm that 

 among the many Argonauts, less than a nut in size, which I 

 have examined, I never found a Hectocotylus. The Hectocotyli 

 of the Tremoctopus were almost all fixed in the mantle-cavity ; 

 a few crept about in its vicinity externally, or lay at the bottom 

 of the vessel in which the Tremoctopus "was contained; since, 

 as Kolliker has stated, they usually leave the dead animal. 



5. Direct testimony that the Hectocotyli play the part of males 

 to their female Cephalopoda is afforded by two observations of 

 a perfect copulation in Tremoctopus. 



Upon the 2nd of August two large specimens of TremoC" 

 topus were brought to me at the same time, each of which carried 

 in its mantle-cavity a Hectocotylus, fixed as usual in the neigh- 

 bourhood of the gills. Upon pouring water on them, it w^as seen 

 that the penis of each was inserted far into the opening of the 

 right oviduct. Both of the Hectocotyli moved vivaciously, and 

 appeared to be very angry that their endeavours w^ere disturbed. 

 Since it was late in the evening I was obliged to defer further 

 examination until the following morning, when I found both in 

 situ, but dead. Both Hectocotyli were distinguished by the 

 length of the penis ; on endeavounng to draw it out of the ovi- 

 duct it was held pretty fast, and if let go was retracted again for 

 a certain distance ; one might so allow half an inch of the penis 

 to glide in and out. This resulted from a very elastic filament, 

 which, from the point of the penis, projected in deeper ; it could 

 be drawn out for an inch from the opening of the oviduct with 

 the penis, and then when it finally gave way it slipped back 

 again. In both cases this thread did not exactly enter at the 

 point of the penis, but somewhat behind ; and then in its further 

 course it could be clearly identified as the inner part of the for- 

 merly-described ductus deferens. 



The right oviduct of the Tremoctopus possessed, besides the 

 chambered gland, two dilatations whose walls were greatly soft- 

 ened. The external enlargement was little larger than upon the 

 left side, and contained, together with mucus, merely a portion 

 of the thread torn off from the penis, which has been mentioned. 

 The second larger expansion contained the very singularly con- 



