296 CRUISE OF THE BARRERA 



possessed by the less dependent males. The vari- 

 ous species of mosquitoes already studied have 

 been known to feed upon the blood of mammals, 

 birds, snakes, and of other insects, and even upon 

 the dead. With such habit one may easily un- 

 derstand the risk of any mosquito-bite. In the 

 particular case of the fever-breeding species it is 

 now known that the malarial protozoan can only 

 complete its life cycle by a residence for a period 

 within the body of the mosquito, and the same is 

 true of the yellow-fever germ. When the proto- 

 zoans are ready for transmission to the next host, 

 they occupy the salivary glands of the mosquito 

 there awaiting their transference into the blood 

 of a mammal where they complete their cycle in 

 the haemoglobin of the blood-corpuscles. 



Bartsch and Greenlaw, dissatisfied with dredg- 

 ing results in the harbor, proceeded in the launch 

 to the narrow entrance and made a number of 

 dredge casts in three to fifteen fathoms, getting 

 but meager returns for their labor. Clapp and I 

 undertook the cleaning, preserving, and stowage 

 of the Guajaibon material, a task occupying the 

 entire morning. Another party went for Cerion 

 and finally all joined for a swim at the sandspit. 



