242 PARTHENOGENESIS VII 



all competent naturalists to be tliorouglily demon- 

 strated, and beyond tlie reach of criticism, yet some 

 more and some less eminent biologists have not been 

 wanting to deny tlie Lucina sine concuhitu, and have 

 raised objections, such as that there is a possibility 

 of error in the experiments in reference to the ex- 

 clusion of males from the supposed parthenogenetic 

 female ; and again, that these so-called females were 

 not demonstrated ''not to be hermaphrodites." In- 

 deed so deeply rooted is the conviction that eggs are 

 made to be impregnated by spermatozoa, and that 

 they then, and then only, can proceed to develop, 

 that Siebold felt it necessary to add to his proofs, 

 in order to establish his position that not only do 

 unimpregnated eggs develop into perfect animals, but 

 that such an event is by no means an exceptional 

 occurrence among certain groups, and has a definitely 

 fixed and orderly recurrence amongst them. He 

 naturally was also anxious to extend the class-limits 

 within which a true parthenogenesis can be said to 

 occur, and he desired to inquire into the sex of the 

 parthenogenetically-produced off'spring in such cases 

 as could be critically and decisively studied. Hence 

 the renewed researches which have extended over 

 several years, the results of which are given in the 

 present brochure. 



Yon Siebold's merit in this and his former work 

 (but more especially in this) is not the enunciation of 

 a new^ theory, or hypothesis, but the great care, 

 ingenuity, and persistence which he has displayed in 

 investigating cases in which for many years collectors, 



