ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 673 



two spheres fused, and a small sphere or droplet appeared 

 above (8: 05 A). This disappeared almost immediately, and a 

 new little droplet broke loose at the right lower side of the 

 egg (8:06). It disappeared in a few seconds, and the egg 

 once more divided, but with an altogether different position 

 of the cleavage plane (8:06^, 8:07i). In a few seconds 

 the two spheres fused into one cell, and 

 a number of small droplets appeared 

 below (8:08). Of course it is impos- 

 sible to tell whether or not these single 

 spheres or droplets contained nuclei. 



r ICr. 160 



These phenomena are of importance for 



the mechanics of development, inasmuch as they show that the 

 bulk of the egg is liquid, and that in the case of Chaetopterus 

 its viscosity is very small, and less than in the case of the 

 sea-urchin's egg. It is hard to understand what kind of 

 structure could be preformed in a liquid mass of such low 

 degree of viscosity beyond the differentiation into nuclear 

 and protoplasmic material and possibly centrosomes. 



The appearance of the trochophores originating from un- 

 fertilized eggs is exactly like that of those arising from fer- 

 tilized eggs, if one compares equal stages of development. 

 Fig. 158 gives no good idea of the trochophore, inasmuch 

 as the latter is at first spherical. Fig. 160 shows two 

 parthenogenetic trochophores, drawn by the camera with 

 the exception of the cilia, which are more or less diagram- 

 matic. The eggs from which these trochophores originated 

 had been treated with KC1. It is hardly necessary to men- 

 tion that the appearance of the trochophores developing 

 from parthenogenetic eggs depends greatly upon the treat- 

 ment the egg had received. I mentioned this point in 

 connection with the artificial parthenogenesis of sea-urchins. 



A point which must be discussed is the duration of 

 life of the parthenogenetic trochophores. All the ChaB- 



