26 Cutler, Parthenogenesis in Animals 



Inheritance in Parthenogenesis. 



The inheritance of characters in parthenogenetic animals has 

 not, up to the present, been greatly investigated. In 1899 

 Warren inquired into the inheritance of the ratio between the 

 length of the protopodite of the antennas and the body length in 

 Daphnia magna. He found that the parental correlation was 

 0-466 ± 0-054 (founded on 23 parents and 96 offspring), and the 

 grandparental one 0-27 ± 012 (founded on 7 grandparents and 

 26 offspring). This denoted that there might be a diminution 

 of the correlation as the ancestral distance was increased, but 

 very few individuals were investigated. Similar results were 

 obtained by investigations made upon the Aphid, Hyalopterus 

 trirhodus. Here the characters employed were (1) distance be- 

 tween the eyes; (2) the length of the right antenna; (3) the ratio 

 of (1) and (2). 



About this time Johannsen published the result of work done 

 with Phaseolus vulgaris. Two characters were chosen for investi- 

 gation, the weight of the beans 1 and fthe ratio between the width 

 and length. All the descendants arising from :a single plant by 

 self-fertilisation were called pure lines, and a number of these 

 pure lines constituted a population. Experiment showed that 

 in such a population the variations followed the normal curve 

 and the correlation between the parent and offspring" was 0-336 

 ±0012. When, however, pure lines were considered the varia- 

 tions still followed the normal curve, but the correlation between 

 the parent and offspring was nil. Further, the deviations of the 

 parents from the mean were not inherited. 



Jennings' extensive work on Paramcecium has in a marked 

 way confirmed these conclusions. 



The recent experiments of Agar are probably the most 

 detailed that have appeared on the subject of inheritance and 

 parthenogenesis. He chose as his animals two species of Simo- 

 cephalus, one species of Daphnia and an Aphid, Macrosiphum 

 antherinii. In the two species of Simoeephalus the character 

 used was the body length measured at the first instar and the 

 first adult instar, and in the species of Daphnia the ratio between 

 the posterior spine of the carapace and the body length. The 

 results of the investigations showed that in a monoclonal popula 

 tion (one known to have descended from a single ancestor) jthe 

 ancestral correlation coefficients were insignificant, also there 

 w.as no trace of Mendelian segregation. In general the conclu- 

 sions were in complete agreement with those of Johannsen. 



In the experiments with the Aphid the characters chosen 

 were those employed by Warren. The ancestral correlation 



