THE ANATOMY OF PENTASTOMUM TEEETIUSCULTJM. 39 



the primaiy papilla, point to their having some important func- 

 tion to perform. It may be noted that they are confined to 

 those parts of the body which come in contact either with («) 

 the host or (b), in the case of the male, some other Penta- 

 stomum. Those in the head region are so placed that they are 

 in contact with the walls of the pit hollowed out in the lung 

 tissue to contain the head of the parasite. The only other 

 ones are the two placed one on either side of the male genital 

 opening (fig. 5). It is easy to see that in P. proboscideum, 

 with their projecting processes, they could act in these positions 

 as organs of touch ; but in other forms such processes are 

 wanting, and the cuticle is continuous over the external 

 surface. 



Judging by the life led by the parasite, an organ of touch — 

 that is, one enabling it to be conscious of contact with external 

 bodies— would be of importance ; v^^hilst it scarcely needs to be 

 provided with more than this, since within the lung it cannot, 

 so to speak, go wrong in piercing the tissues in search of 

 food. 



These organs are probably sensitive to such stimuli, for 

 example, as those produced by the flow of blood through 

 vessels close to them, a stoppage in the flow, and hence in the 

 food supply of the parasite, being detected. When this takes 

 place the parasites doubtless relax their hold of the tissues, and 

 wander away in search of parts where the sense-organs are 

 aff'ected in the normal manner by the flow of blood, &c. If 

 the host be dead they may thus naturally wander out from the 

 lung, in the characteristic way in which parasites leave the 

 body of a dead host. 



9. Reproductive Organs. 



(Figs. 6, 7, Sections A— G; figs. 11—26, 37, 40—46, 48, 

 55—58, 60, 62—68.) 



(1) Female. — In the diff"erent forms the anatomy of which 

 has as yet been studied the female organs appear to agree 



