GENERATIVE SYSTEM OF THE ANNELIDANS. 273 



condition in the ovary or the testicle, break loose into the abdominal 

 cavity, where, insulated from all the solid parts, and without any con- 

 nexion with the vascular system, they undergo all the principal phases of 

 their development. " It appears," says M. de Quatrefages, " that the 

 liquid which thus bathes them on all sides must be vitalized, and that it is 

 from it that they receive the materials necessary to enable them to grow 

 to ten times their original size ; in fact, this fluid acts the part of an 

 ovary and of a testis to them. The liquid enclosed in the general cavity 

 of the body of the Annelidans is therefore in some respects a fluid organ." 



(700.) The spermatogenous masses floating in the fluid contained in 

 the general cavity of this Annelid are irregularly ovoid, and present 

 themselves, as is usual, in different stages of development. At first 

 they are perfectly diaphanous, smooth, and manifestly homogeneous, 

 without any trace of an enveloping membrane. The dimensions attained 

 by them in this condition reach to as much as y^-th of a millimetre in 

 length, and J^rd of a millimetre in breadth. 



(701.) At this epoch they may be seen to exhibit two grooves, cross- 

 ing each other at a right angle, and whose direction does not appear to 

 present any constant relation with the form of the mass itself. The 

 number of grooves soon increases, and they become more marked and 

 deeper, and the mass, after having presented a surface subdivided into 

 large irregular lobes, assumes a mulberry-like aspect, and ultimately 

 becomes completely granular. During the time that these phenomena 

 are being manifested, the mass continues to increase in volume, and in 

 its ultimate condition it is sometimes -jL-th of a millimetre long by nearly 

 of a millimetre broad. 



(702.) The masses, when a little further advanced, split up, and the tail 

 of the spermatozoids is then apparent. The spermatozoids continue to 

 adhere together for some time longer by their bodies, as well as to the 

 granulations not yet transformed : ultimately they are gradually separated. 



(703.) At the moment when the spermatozoids separate themselves 

 from the minute masses of which they constitute a part, their body is 

 almost fusiform, and perhaps not more than yjjoth of a millim. long and 

 ^Jj-yth of a millim. thick ; but they grow during the time they remain 

 in the fluid that bathes them: the body and the tail elongate, and, 

 besides this, the former increases considerably in its transverse dia- 

 meter. Among spermatozoids quite mature, some will have attained to 

 a length of g^th of a millim., and a breadth of -j-T^yth of a millim. 



(704.) According to Dr. Williams*, here, as elsewhere throughout the 

 class of Annelidans, the segmental organs are to be regarded as the 

 primary parts of the reproductive system. Throughout the Nereid 

 group, the ciliated, horseshoe-shaped segmental organ exists. It con- 

 sists of a tube, highly ciliated, both ends of which communicate with 

 the exterior : the ingoing limbs are situated in the immediate vicinity of 

 * Phil. Trans. 1858, p. 124. 



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