116 



LIFE-HISTORY OF PARASITES. 



their development ; that is, they resemble forms to which the para- 

 sitic Nematodes bear relations, which have led us above to regard 

 them as their forerunners, and which are often seen represented in 

 their young forms. An exception must be made in the case of a 

 single very peculiar species (Sphcrrularia), which lives in the body- 



FlG. 74. Aspidoyastcr conchicda. (A.) Embryo, 

 \B. ) Young animal, not yet sexually mature, 

 (after Aubert). 



FIG. IS.Archigetes Siebddi. 



cavity of the hibernating humble-bee, and shows relations of organi- 

 zation which are as yet only incompletely understood. 1 Likewise 



1 See especially Sir John Lubbock, Natur. Hit. Rev., vol. i., p. 44, 1861, and 

 Schneider, " Monogr. d. Nematoden," p. 322, whose opinions regarding the life-history 

 and morphology of this strange worm differ widely from each other. [Recent investigations 

 of Schneider (Zool. Beitrage, Bd. i. , p. 1, 1884) have made us acquainted with the interesting 

 fact that the young Sphctrularia grows outside the body of its host into a sexually mature 

 animal, resembling Anyuillula, without essential change in its organization. I have con- 

 vinced myself of the correctness of this observation, and believe I have obtained proof that 

 these worms copulate while in the free condition, and that only the females find their way 

 into the humble-bees, where they develop into the paradoxical Sphcerularia. If such be 

 the case, Sphcvrularia can no longer be considered an exception to the rule above stated. 

 R. L.] 



