114 SEXUAL ORGANS. 



sexual union took place. He immediately examined the female 

 again, and found the mouth surrounded by spermatophores 

 attached to the buccal membrane. After this examination, the 

 animal was permitted to continue ovipositing, which she did for 

 more than two hours. It is evident, says M. Lafont, that these 

 spermatophores serve to fecundate the eggs at the moment when 

 they pass out of the siphon and when the female takes them 

 between her arms. Since that period more than half of the 

 females of Sepia and nearly all those of Loligo that he has 

 examined, were found to carry a greater or less quantity of 

 spermatophores around their mouth. 



Steenstrup has shown (Ann. Mag. Nat. Hist., 2 ser., xx, 1851) 

 that whilst the octopods (which alone are known to lose their 

 copulatory arm) possess in the highest degree the power to 

 reproduce mutilated members ; the decapods, on the contrary, a,re 

 not able to remedy such losses by a new growth ; and this is a 

 cogent reason for believing that the process of fecundation is 

 entirely different in the two groups. Steenstrup states that the 

 hectocotylized arms, so far as he can ascertain, present no 

 changes at the season of copulation, that they present the same 

 features in small as in large individuals ; and he assumes that 

 when the young male leaves the egg it is already furnished with 

 the hectocotylized arm proper to its species. 



Braun has supposed the aptychi to be the shells of the males 

 of Ammonites, instead of opercula ; thus he explains why they 

 are so often found at the base of the first chamber of Am- 

 monites. The opinion has more recently been advanced that 

 the aptychi were protective organs of the nidimentary glands 

 of female Ammonites. 



,M. Ussow observes that the spawning time of Argonauta 

 lasts from May to August ; of Loligo, Sepiola and Ommas- 

 trephes, from March to June ; but he has obtained mature ova 

 of Sepia in Naples almost all the year round, except in August. 

 . — TJssow, " Development of Cephalopoda," Ann. Mag. N. S., 4 

 ser., XV, 1875. 



I have figured a few forms of egg-clusters (xviii, 12-15) : 

 unfortunately the eggs of the Nautilus are not known, so that our 

 knowledge is confined to the dibranchiates. Of these the most 

 curious is the Argonaut, the elegant shelly structure of which 

 originates, as we have seen, from the expanded dorsal arms of 

 the female which cover its sides and form the only attachment 

 of the animal to it. In the unoccupied hollow of the spire are 

 attached the minute clustered eggs (xviii, 15), and its special 

 function appears to be for their protection during development. 

 Each egg is separately enclosed in a rounded shell, which is 

 furAished with a long, thin membrane of attachment. We know 

 but little of the eggs of Octopus : Aristotle describes them as 



