96 George Lefevre 



unfertilized eggs with solutionsof KCl. Inthis case differentiated, 

 ciliated structures may also arise without segmentation, and pseudo- 

 cleavages, involving only the cytoplasm, are of frequent occurrence. 

 Ciliated embryos, however, may also be produced as the result of a 

 cleavage process, in which both cytoplasm and nucleus are con- 

 cerned, but here cell-division is quite abnormal. Fusion of sepa- 

 rate eggs was observed in Podarke, but it is rarer than inChaetop- 

 terus and fewer eggs unite into a common mass. 



Bullot ('04), experimenting with the eggs of an annelid, Ophelia, 

 has obtained results which are not in accord with those just cited, 

 in that he has shown that the parthenogenetic larvae of this worm, 

 produced by solutions of KCl and NaCl, arise only from seg- 

 menting eggs. How nearly normal the processes of cleavage and 

 differentiation are in this case cannot be determined from the 

 inadequate figures and description given, although he states that 

 "the divisions go on regularly into four, eight, sixteen, and more 

 cells," and that later a blastula of characteristic shape is formed. 



Lastly, Scott ('06) has studied the morphological phenomena of 

 parthenogenesis in the eggs of Amphitrite which were subjected to 

 the action of salt solutions, especially solutions of Ca (NO 3) a, and 

 to mechanical agitation. Usually from 5 to 25 per cent of swim- 

 ming structures were obtained. He found that certain differen- 

 tiations may occur with or without cleavage and with or without 

 the formation of polar bodies. Cleavage of the egg may take 

 place, but it is generally abnormal, always so in later stages. A 

 ciliated body is produced, which may show more or less extensive 

 cell divisions but usually exhibits no true segmentation; the 

 mass may, however, contain many nuclei. In no instance was 

 anything remotely approaching a normal larva obtained, although 

 certain cytoplasmic differentiations were present, as the develop- 

 ment of an ectoplasmic layer, the growth of cilia, and the appear- 

 ance of vacuoles and pigment. 



It is clear, then, that the previous work on artificial partheno- 

 genesis of annelids, with the methods which have been employed, 

 has shown little in common with the processes of normal develop- 

 ment, and that at best a ciliated structure has been produced which 

 exhibits certain specialized regions of the cytoplasm but no nor- 



