866 



LOJVER INVERTEBRATES. 



larger than the rest, which the male then charges with one of the packets of sper- 

 matozoa soon to be described. During the coitus this arm becomes detached and 



Fig. 480. — Heotocotylization in the male Argonmtta ; in A is shown the sac which in B has burst 

 open, allowing the hectocotylized arm to extend itself. 



remains adherent to the female, which then swims away. A new arm is formed in 



the male before the return of tlie breeding season. 



This subject of heotocotylization has been studied by Steenstrup, a Danish nat- 

 uralist, who finds that the arm or extent of modification is 

 variable in the different genera, but in some (among which is 

 Omniastrephes, so common on our coast) this process has not 

 been observed. We have just alluded to the 

 packets of spermatozoa. These are called 

 sperraatophores and are found variously mod- 

 ified in different invertebrates. In Loligo, one 

 of the squids which we select as a type, it con- 

 sists of a slender capsule about half an inch in 

 length, two thirds of which is occupied by the 

 spermatozoa, while the remainder contains a 

 complicated discharging apparatus. On con- 

 tact with the salt water the sheath ruptures 

 at one end, and forth issues the discharging 

 apparatus, dragging the spermatozoa after it. 

 The eggs of the cephalopods are usually 

 Zn«<7o; ra, sheath; 6' packet enveloped in capsulcs, some of which contain 



of spermatozoa; c, disoharg- ^ r ' 



ing apparatus; d, a single as many as two hundred earffs. This is not 



spermatozoan. '' '~'~ 



the case with all, for the writer once dredged 

 the eggs of an unknown cephalopod (? Rossia) which were separate 

 and deposited free upon the ocean's bottom. They were about the 

 size of a small pea. The shape and size of the capsules vary consider- 

 ably. Those most commonly found on the New England coasts are 

 those of Loligo pealei. They arc finger-shaped and gelatinous, and so transparent 

 that the embryos can be readily seen. Usually from twenty-five to a hundred of these 



Fio. 481. — Spermatophore of 



Fig. 4S2.— Egg cap- 

 sule of Loligo, 



