LAR VAL DE VEL 0PM EN 7\ 



153 



so as to make a projection into the myocoel in front (Fig. 

 86 B, C}. This projection of the primitive gonad into the 

 myocoel next in front of that to which it originally belonged, 

 is gradually carried to such an 

 extent that the gonad becomes 

 entirely shut off from its original 

 myocoel and hangs freely into the 

 next one, being connected by a 



Short Stalk with the anterior face Fig. 87. Similar prepara- 

 tion as the preceding, showing 



of the dissepiment and surrounded a later stag e i n the development 

 by a membrane which is obviously B ^ e R j mitive gonad ' (After 

 derived from, and for some time 



continuous with, the original dissepiment (Fig. 87). In 

 correlation with the increase in size of the primitive gonad, 

 an evagination of the basal wall of the myocoel in which it 

 now lies, takes place, and by the time the young Amphi- 



Fig. 88. Preparation showing the rhomboidal pouches of the myoccel 

 which project into the atrial cavity. (After BOVERI.) 

 This condition is found in individuals of 13-14 mm. 



oxus has attained a length of 13 or 14 mm. there is, in 

 connexion with each primitive gonad, a wide rhomboidal 

 expansion of the lower portion of each corresponding 

 myoccel projecting into the atrial cavity (Fig. 88). 



The cavity of these sacs, to the wall of which the gonads 

 are at this stage still united by a stalk, constitutes the so- 

 called perigonadial cceloni^- or cavity of the gonadic 

 pouches, which, at the time of sexual maturity, is entirely 

 filled up by the sexual elements. 



