ARTIFICIAL PARTHENOGENESIS IN THE 

 SILKWORM. 



VERNON L. KELLOGG. 



I may be pardoned, because of the brevity of this paper, for 

 recalling attention to a subject that seems (but is not) pretty well 

 worn. Really only three men (Tichomiroff, Verson and Quajat) 

 have contributed the data of observation and experiment which 

 have furnished the literature of parthenogenesis with such a host 

 of fleeting references that it must seem to the casual reader as if 

 silkworm parthenogenesis had been investigated only less than 

 that of the sea-urchins. As a matter of fact it has been investi- 

 gated (the work described in the present notes included) but 

 little. 



In a clutch of unfertilized eggs oviposited by a virgin silkworm 

 moth {Bombyx mori) almost always a small number of eggs be- 

 gins development. This development extends to the formation 

 of the embryonic envelops and sometimes farther, and is clearly 

 indicated to the observer by the change in color of the egg from 

 yellow to cherry or through cherry to gray. Non-developing 

 eggs remain yellow and, after a while, collapse. Eggs which 

 begin to develop either persist in spherical shape, which indicates 

 persisting life, or collapse, which means death. The development 

 of unfertilized eggs rarely proceeds, without artificial stimulus, 

 beyond a very early embryonic stage. In fully 500 clutches or 

 broods of unfertilized eggs (from confined females from isolated 

 cocoons) under observation, not a single egg gave up its larva, 

 although an average of about seven or eight per centum of the 

 eggs began to develop. 



Although this parthenogenetic development always ceases and 

 the embryo dies before reaching hatching stage, much difference 

 in vitality or duration of life of the egg (strictly, embryo) is notice- 

 able. Some of the developing eggs collapse within a few days, 

 some in a few weeks, while a few persist for several months. 

 (The normal egg stage, i. e., time from egg laying to hatching 

 of larvae in the silkworm univoltin races, is about nine months.) 



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