60 MUL.LER ON THE MALE OF 



ance figured by Kolliker (pi. 2. fig. 19) arose: only the ap- 

 pendage was free, while in KoUiker's specimen it was inserted 

 in the pigmented capsule. 



We may hence assume that the semen during ejaculation passes 

 from the thicker sac towards the point of the appendage*. It agrees 

 very well with this conclusion, that a copulation very probably 

 takes place during which the appendage represents the penis 

 (vide infra). KoUiker's Hectocotylus therefore only committed 

 an error loci when it deposited its semen in the pigmented cap- 

 sule. The presence of an investment to the seminal coil which 

 Kolliker found in the pigment-capsule, is not, as I believed at 

 first, any argument against its secondary deposition there, for a 

 structureless layer was also very visible in the free seminal cy- 

 linder, at least in some portions of it. It is perhaps only 

 analogous to the structureless mass which is to be found else- 

 where in the sexual canals of the Cephalopoda, and is deposited 

 around the semen when excreted. In a second instance I could 

 find no such investment. 



Since the pigmented capsule upon the back of the Hectoco- 

 tylus could not be the testis, the latter was to be sought for 

 elsewhere. At first, I was tempted to consider the silvery sac 

 as its representative ; since not only was this full of perfect 

 spermatozoa in all free Hectocotyli, but also in that Hectocotylus- 

 arm already referred to which had burst its sac after its spon- 

 taneous detachment. Nevertheless it was surprising that in 

 other Hectocotylus-arms just taken out of their sac, the silvery 

 capsule had not its white colour, and neither perfect semen nor 

 any stages of its development were to be perceived therein. 



Subsequently I convinced myself that there is unquestionably 

 a testis in the abdomen of the animal which carries the Hectoco- 

 tylus as an arm. Behind the gills and venous appendages a 

 great part of the mantle- cavity is taken up by a capsule, whose 

 free lower wall is very remarkable on account of its isolated 

 chromatophora scattered over as hining golden ground. Behind, 



* In most cases I could not exactly make out the place of the aperture, though 

 in the two upper thirds of the appendage the ductus deferens is usually easily 

 recognizable, and even far forward has a diameter of 0*05 of a line when it is 

 not collapsed. On one occasion I succeeded in pressing the semen from the 

 silvery sac to within two lines of the point where the ductus deferens only 

 measured 003 of a line. 



