A Cytological Study of Artificial Parthenogenesis 

 in Strongylocentrotus purpuratus 1 ). 



By 

 Edward Kindle. 



With Plate V. 



Eingegangen am 14. Mai 1910. 



Introduction. 



The following investigation was undertaken mainly with the 

 object of tracing the cytological changes that follow the chemical 

 fertilization 2 ) of sea-urchin eggs by treatment with a monobasic 

 fatty acid, followed by treatment with a hypertonic salt solution 

 (LOEB, '05, '09). 



With this method LOEB has shown that it is possible to obtain 

 from the unfertilized eggs of echinoids practically 100 per cent of 

 larvae, a large percentage of which are normal. In external features 

 the process of development is almost identical with that occurring 

 in normally fertilized eggs and, therefore, it is of interest to deter- 

 mine whether the cytological changes are also similar to those that 

 ordinarily follow the entrance of a sperm into the ovum. 



The cytological effects of various solutions, mainly on the eggs 

 of echinoderms, have been investigated by a number of authors. 



R. HERTWIG ('96) studied the effect of dilute solutions of strychnine 

 on the unfertilized eggs of Echinus and SphaerecMnus, and found that 

 the nucleus, after this treatment, may give rise to a typical mitotic 

 spindle in which division of the chromosomes takes place. The 



!) A thesis submitted in partial fulfillment of the requirements for the 

 degree of Doctor of Philosophy at the University of California. Berkeley, 

 May, 1910. 



2 ) For the sake of brevity the term > Chemical fertilization* is employed 

 to denote the starting of development in unfertilized eggs by chemical means. 



ArcMv f. Entwicklungsmechanik. XXXI. 10 



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