Artificial Parthenogenesis in Thalassema Melhta 95 



Mead ('95, '98b) had already shown that the germinal vesicle of 

 ChcCtopterus breaks down when the egg comes in contact with sea- 

 water; the first maturation spindle forms, and the chromosomes 

 pass into the equatorial plate, but the mitosis is not completed 

 unless fertilization takes place. He also discovered the important 

 fact that the addition of a small quantity of KCl to the sea-water 

 produces the same effect as the spermatozoon, causing the extru- 

 sion of the polar bodies, the formation of the yolk lobe, and other 

 changes in the egg preparatory to the first cleavage ('98a, p. 213). 

 Lillie, however, extended these observations,andfound that, after 

 exposure for about one hour to solutions of KCl in definite con- 

 centration, the unfertilized eggs of Chaetopterus may undergo a 

 process of cytoplasmic differentiation unaccompanied by cell 

 division, and in about twenty-four hours after the beginning of the 

 experiment give rise to ciliated structures which in some cases 

 more or less simulate the appearance of trochophores. They 

 usually contain but a single nuclear area, and the cytoplasm is 

 differentiated into a ciliated ectoplasm and a yolk-laden endoplasm 

 which are comparable with the ectoderm and endoderm of the 

 trochophore. Since the KCl solutions cause a disintegration and 

 ultimate disappearance of the cell membrane, the naked cytoplasm 

 is left unprotected, and fusion-phenomena between different eggs 

 are of common occurrence, as Loeb ('01) had previously observed, 

 the agglutination being greatly increased by the addition of a small 

 quantity of CaClz to the K-containing sea-water. In harmony 

 wuth the results of Loeb, Lillie also observed that the period pre- 

 ceding differentiation of the cytoplasm is characterized by amoe- 

 boid movements which may exhibit an astonishing degree of activ- 

 ity. If cleavage takes place at all, as it does in some eggs, it rarely 

 goes very far, and only in a small proportion of such eggs does 

 cell division approximate the normal. Division of the cytoplasm 

 •unassociated with nuclear division is of common occurrence, the 

 non-nucleated portions of protoplasm always fusing sooner or 

 later with the general mass. A comparison of my own results with 

 the observations and conclusions of Lillie will be made further on. 

 Results essentially similar to those of Lillie have been obtained 

 by Treadwell ('02) in Podarke obscura after treatment of the 



