32 W. BALDWIN SPENOEE. 



or else the body-cavity of the Pentastomum contaius a blood- 

 red fluid such as is uot kuown in auy other Arthropod. 



Doubtless; iu passing through the canal walls, the blood 

 undergoes some change, but finally it bathes all the organs of 

 the body. The latter must be able, as are the various struc- 

 tures in a Cestode, to obtain from the fluid which permeates 

 them nutritive material, and according to their nature we may 

 suppose that they withdraw certain elements, some of which, 

 according to the nature of the organ, are used to build up new 

 structures, whilst others, useless to the body, are excreted. 



The latter function is probably performed by the stigmatic 

 glands, which are widely scattered over the body and open 

 directly to the exterior. Very different in nature from these 

 are, however, the hook- and head- glands, and their function is 

 probably, as above suggested, that of secreting from the blood 

 a fluid material which has the power — just as in the case of 

 the so-called salivary glands of Hirudo — of preventing the 

 coagulation of the blood. 



Leuckart^ suggested that the function of these glands was 

 that of producing an irritant material which, when passed out, 

 resulted in the organ in which the Pentastomum was parasite, 

 giving out a larger supply of nutrient material. Now in 

 P. teretiusculum there is no need, when once the tissues 

 are pierced, of any irritant organ to cause a flow of blood. 

 There is, however, a want of some structure which shall 

 prevent the coagulation of the blood. 



Hoyle has suggested that the stigmatic glands may serve to 

 secrete a material which forms the cocoon in the young state. 

 Possibly this may be so, but they are so highly developed iu 

 the adult form that they must subserve some special function 

 in the latter, and the only likely one appears to be that of 

 excreting material useless to the animal. 



' Loc. cit., p. 06. 



