225 



carried further in Sjnbranciiiis than in Monopterus, just as in the 

 former the whole curious development of the fore-brain has reached 

 a further stage than in the latter, as was already pointed out in 

 discussing the sulcus limitans telencephali. The same thing is also 

 clear in considering the caudal end of the striata. In Monopterus 

 the striatum is still separated by a part of the septum from the 

 ventriculus medianus and the recessus praeopticus. The lateral 

 portions of the striata extend equally far caudally as the median 

 portion ; in the series of sections the striatum is therefore seen to 

 disappear entirely simultaneously, and at the back it is covered by 

 the septum and the lateral portions of the cerebrum, which meet here. 

 In Synbranchus, on the contrary, the striatum in the middle pushes 

 away the ventral portion of the septum, so that the striatum lies 

 directly dorsally from the recessus praeopticus (tig. 6). This median 

 portion of the striata extends further in a caudal direction than the 

 lateral parts. At the back of the fore-brain the striatum is not 



sulc.lim.tel. 



sulc.yps.p.post 



striatum 



rec praeopt 



epistnatum 

 • lino post. 



tr. stn.thal 



tr.olf.med 

 plat 



tP.hypoth oirmc' 

 tn. olRttial.p.ventr. 



nuci, praeopt. p. m 

 nud.ppaeopt p.p 



n.opt. 

 tn.olf thal.p.dors. 



Fig. 5- Monopterus albus. 



tr. teniae. 



