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R. T. GUNTHER. 



ing animals, nor is there any reason to suppose that their 

 recent ancestors (like those of the Heteropoda) were so, or, 

 indeed that they have ever had a creeping ancestor at all. 

 On the other hand the circumoral hood, " Kappe " or 

 " prepuce," situated, as it is, between the head and visceral 

 regions, occupies the same relative position as the "foot" of 

 a Dibranchiate Cephalopod, or the lateral lobes of Nautilus, 

 and to these structures we desire to compare it. The method 



Text-iig. 3. — Tremoctopus (from Pelseneer, after Joubiu). 

 Note the interbrachial membrane. 



of innervation would, no doubt, settle the question of the 

 homology of these organs easily were the hood a more power- 

 fully developed muscular organ than it is. According to our 

 theory the Ch^etognath " hood " is the Cephalopod circum- 

 oral foot in its most primitive condition, or else it represents 

 that organ in a reduced condition as a mere reduplica- 

 ture of the ectoderm into which the body cavity extends but 

 a short distance. It is therefore to be compared with the 

 interbrachial membrane of many of the Cephalopoda (llistio- 



