MORPHOLOGY OF CYCLOSÏOMATA. 870 



I have made out. From the region of the liver-aulage backward 

 the development of the duct is irregular ; he says : " Auf der 

 einen Seite zeigt sich seine Anlage noch rinnen förmig, während 

 sie auf der andern Seite schon vollkoniinen röhrenförmig ab- 

 geschnürt ist. Endlich wechselt dies Verhalten auch auf derselben 

 Körperseite, so dass derselbe Gang, von der Lebergegend rück- 

 wärts verfolgt, bald rinnen-, bald röhrenförmig, geschlossen oder 

 mit offener Lichtung sich darstellt " {loco cit.^ p. ÖQ). The hind 

 end of the duct opens in the cloaca (Afterdarm) by the fusion of 

 their walls and by the communication of the lumen of the duct and 

 the diverticulum of the cloaca. I have not observed in any stage 

 of my embryos examined the numerous convolutions of the seg- 

 mental duct demonstrated by Goette in the region immediately 

 behind the " ursprüngliche Kopfniere." 



Goette has made out the three " peritoneale Scheidewände," 

 as he calls them : two respectively in the anterior and the posterior 

 end of the pTonephros, and the third on either side of the liver. 

 Later, the first contributes, according to him, to the formation of 

 the hind wall of the branchial pouch (Kieraentasche) ; the second 

 is converted into " eine Venenbrücke zwischen dem Sinus 

 venosus and der Leibeswand," while the tliird disappears without 

 leaving a trace. They are, according to Goette, homologous 

 with the " Schlussplatte " of the pronephros in Teleostei ; con- 

 sidered phylogenetically, nevertheless, they have no intimate 

 relation to the pronephros in Petromyzon {loco cit., pp. 56-61). 

 This structure is, as stated on p. 349, doubtless the same as the 

 uppermost peritoneal partition which I have found in my em- 

 bi'yos. I have nothing to communicate on its signiücauce ; 

 but I feel sure tliat his statement is not accurate when he says 

 the structure appears earlier than the ])runeplirüs ; for his ligs. 



