SOFT PARTS AND MECHANISM OF THE PROBOSCIS. 395 



appearance first described by Anthony* and subsequently 

 independently by Wrightf as suckers ; each appears as if 

 closed by a thin membrane. 



In Anthony's figure these membranes are represented pro- 

 truding as sucker-like organs which he described as having the 

 appearance of ' mouse ears,' or ' bat's ears.' I have observed a 

 similar appearance in surface views of the oral disc of the 

 proboscis, but more commonly these so-called suckers appear 

 as they do in Wright's photograph (PL XXIII. , Fig 2). 



Sections of the oral lobes throw light on the true nature of 

 these ' suckers.' Fig. 50 (j and ^) shows the disposition of the 

 thin cuticle between the fork of a ring ; it forms a little sac (s) 

 by the side of the pseudo-tracheal channel. Now, it is mani- 

 fest that such a sac would be easily everted, and it would then 

 present the appearance described by Anthony ; or, if partially 

 everted, the appearance shown in Wright's photograph. 



Between the pseudo-tracheae, and covered by inflections of 

 the hypodermis, a series of tendinous cords extend from the 

 discal sclerite to the edge of the oral disc. These tendinous 

 cords were first described by me [62, p. 49], but perhaps rather 

 indefinitely. Kraepelin describes and figures them. 



These cords are dissolved by boiling caustic potash, but do 

 not seem to be affected by dilute acetic acid ; they are de- 

 veloped from fusiform cells. The paraphysal muscles are 

 inserted into them near their origin, so that they are probably 

 inelastic and act as tendons. 



c. The Mechanism by which the Proboscis is Extended and 



Erected. 



It is quite certain that the retraction of the proboscis and the 

 movements of the haustellum upon the rostrum are muscular 

 acts, but it is also very evident that there are no muscles 

 capable of exserting the proboscis. This fact has already been 

 noticed by Gleichen [3], Macloskie [64], Dimmock [68], and 



* Monthly Micros. Journ., vol. xi., p. 242, 1874. 



t Journ. Royal Micros. Soc., ser. ii., vol. iv., p. 1003, 1884. 



