Prof. H. Karsten on Rhynchoprion penetrans. 299 



For we may easily be convinced that eggs alone, and never 

 larvse, are contained in the female flea, and that the most perfect 

 of these lie nearest to the cloaca ; and any one who has frequently 

 had to remove the dilated female from the skin will have re- 

 marked the projection of a perfectly mature egg from the body 

 of the mother on the slightest pressure being applied to the 

 latter with the needle, &c. The very numerous ovicells which 

 occur in the cylindrical tubes of the simply furcate ovary are 

 gradually developed in such a manner that the most mature egg is 

 always situated next to the issue, and is driven forth by the pres- 

 sure of the other growing ova before the process of segmentation 

 or any other commencement of embryonal development has taken 

 place. In this way the parent animal remains within the skin 

 without any further enlargement until all the eggs are developed 

 and deposited, after which, no doubt, the evacuated and shrivelled 

 body is finally thrown off with the epidermis during the advanc- 

 ing development of the skin — an opinion which might perhaps 

 be fortified by the statements of Rengger (p. 110) and Burmei- 

 ster (p. 126). 



Rengger's statement that the mature egg-sac separates from 

 the organism which has furnished it with nutriment, and that 

 then, in a few days, a number of larvae creep out of it, is refuted 

 at once by the mode of lodgment and the constant enclosure of 

 the body of the Flea in the skin. 



The extraction of the parasite from the skin is, as stated by 

 Gumilla, far more easily effected at a later period than in the 

 first hours and during the penetration, because then the animal, 

 which is working briskly, only increases its efforts by the aid of 

 its mandibles, which are peculiarly adapted for the purpose, and, 

 indeed, fastens these so firmly in the skin that they are not un- 

 frequently torn away from the body of the Flea, and remain 

 sticking in the skin, when the animal is removed with violence. 

 As early as the next day the voluntary activity of the animal is 

 much diminished, and then, but with still more certainty after 

 the lapse of a few days, with a little care the epidermis may 

 readily be pushed aside with a blunt knife or a needle, all round 

 the Flea without injuring the latter, and thus the globular 

 animal may be so far exposed that these instruments or a fine 

 pair of forceps may be got under its body, and it may then be 

 removed without much resistance and by slight pressure, with 

 all the buccal organs, which project far into the true skin (the 

 rootlets or filaments of Sloane, Ulloa, and Schwartz). But if, in 

 removing the dilated and delicate body which adheres more or 

 less closely to the surrounding cellular tissue of the skin, we 

 proceed so clumsily as to tear it, so that a portion of it, with the 

 piercing-apparatus imbedded in the corium, is left behind in the 



