Fasten, Partlienogenetic Data. 
71 
3. Variation among Parthenogenetic Forms. 
Weismann claimed that considerable range of variation 
occured where individuals were produced through a sexual process. 
Recent investigation, however, has disclosed the fact that there 
may be as much variability among parthenogenetic forms as in 
those producing sexually. 
Warren (’96, ’97, ’02), found that in the Aphid Hyalopterus 
trirhodus and in the Crustacean Dciphnia, the parthenogentic 
forms show a marked degree of variability. 
Casteel and Phillips (1903), showed that the drones result¬ 
ing from the unfertilized eggs are even more variable than the 
sexual females. 
Kellogg (’03), has also produced some very interesting meas¬ 
urements in insects, which tend to show that variation among par¬ 
thenogenetic forms is as,well marked as in sexual individuals. 
c: ARTIFICIAL PARTHENOGENESIS. 
Professor Jaques Loeb may be said to be the pioneer in this 
field of experimental zoology. His work on artificial parthenogen¬ 
esis, begun some twelve years ago, has given us a better insight into 
the problem of fertilization. Loeb, in 1899, succeeded in develop¬ 
ing plutei from the fertilized eggs of the sea urchin, when the-, 
concentration of sea water was raised about forty to fifty per 
cent, through the addition of sugar or salt solutions. When the 
unfertilized eggs were put into a hypertonic solution of sea water, 
they shrunk, through loss of water, and underwent a process of 
development. However, no fertilization membrane was brought 
forth. 
In another series of experiments, Loeb exposed unfertilized 
eggs of Strongylocentrotus to a mixture of sea water concen¬ 
trated with a fatty acid, e. g. butyric, acetic, formic, or the like, 
(50 c. c. sea water plus 3 c. c. n/10 fatty acid), and after allow¬ 
ing them to remain in this solution for about a minute, he then 
transferred them to normal sea water, and almost immediately a 
fertilization membrane appeared. These eggs underwent but little 
development, and soon disintegrated. On the other hand, when 
the eggs were placed into a hypertonic solution of sea water, con¬ 
sisting of 100 c. c. of sea water to which 15 c. c. of 2l4n. NaCi was 
