The Cambridge natural history . mes hectocoty-lised. At first it is entirely enveloped in a kind of cyst, in sucha way that only a small portion of the tip projects; subsequentlythe cyst parts asunder, and allows the arm to become expandedto its full length, which considerably exceeds that of the otherarms. At a certain point the acetabula or suckers terminate,and the remainder of the arm consists of a very long, tapering,sometimes thread-like filament, which is pointed at the extremetip. It is not yet knowji how the spermatophores find their way 138 THE HECTOCOTYLUS ARM IN CEPHALOPODA into th
The Cambridge natural history . mes hectocoty-lised. At first it is entirely enveloped in a kind of cyst, in sucha way that only a small portion of the tip projects; subsequentlythe cyst parts asunder, and allows the arm to become expandedto its full length, which considerably exceeds that of the otherarms. At a certain point the acetabula or suckers terminate,and the remainder of the arm consists of a very long, tapering,sometimes thread-like filament, which is pointed at the extremetip. It is not yet knowji how the spermatophores find their way 138 THE HECTOCOTYLUS ARM IN CEPHALOPODA into the hectocotylus, or how tlie liectocotyhis impregnates theova of the female. The arm thns affected is not always thesame. In Tremoctopus it is the third of the right side, in theDccapoda tlie modification usually affects the fourth of the left. This singular property of the male Cephalopoda has onlyrecently been satisfactorily explained. It is true that Aristotle,more than twenty-two centuries ago, distinctly stated that certain. Fig. T<\ .—Male of Onjthoc iuhercu-lataRaf. ( = Philonexis catenu-latus, Fer.), Mediterranean,showing three stages, A, B,and C, iu the deveh)pment ofthe hectocotylus arm: ,hectocotylus still in the cyst ;cy, spoon-shaped cyst at theend of the arm when freed ;th, thread-like organ freed bythe rupture of cy. Naturalsize. From specimens in theBritish Museum. of the arms were modified for sexual purposes. Speaking ofwhat he calls the polypus (which appears to represent the Octojinsindgaris of the Mediterranean), he says: It differs from thefemale in having what the fishermen call the white sexual organon its arm ; again, Some say that the male has something of asexual nature {alhoLwhh rt) on one of its arms, that on whichthe largest suckers occur; that this is a kind of muscularappendage attached to the middle of the arm, and that it is V THE HECTOCOTYLUS ARM IN CEPHALOPODA I 39 entirely introduced within the funnel of the female. Unfor-tunately th
Size: 1208px × 2068px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
