ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 671 



on the right side the development of the unfertilized eggs. 

 At about the same time a drawing of the fertilized and 

 the unfertilized K eggs was made. At 12:45 some of the 

 fertilized eggs were found in the four- to eight-cell stage. 

 The unfertilized eggs were only amoeboid at that time. 

 Some of them (see Fig. 158) at 12:55 showed an incision, as 

 if they were about to divide. At 1 : 20 some of the fertilized 

 eggs had reached the sixteen-cell stage, and at -1 : 30 only a few 

 eggs were found among the K eggs that seemed to be seg- 

 mented. At 2 : 10 the fertilized eggs were in an advanced 

 stage of cell-division, while the K eggs were not distinctly 

 segmented. At 3:40 the fertilized eggs had reached the 

 trochophore stage, with a clear edge and a dark center. At 

 that time the most differentiated eggs of the parthenogenetic 

 lot were in the condition that is represented at 3:15 in Fig. 

 158. At 4:30 we find these eggs still in the same condition, 

 and not until 7:40 did the parthenogenetic eggs reach the 

 beginning of the trochophore stage clear edge and dark 

 center (Fig. 158). The fertilized eggs had formed their 

 cilia, and at about 5 o'clock were swimming around, while 

 the K eggs did not begin to swim until 8 or 9 o'clock. The 

 unfertilized control eggs which had remained in normal sea- 

 water during this time were at 8 o'clock still absolutely 

 spherical, and had given no signs of development of change. 

 Although the drawings in Fig. 158 give an idea of the 

 development of the parthenogenetic eggs, this idea has to be 

 supplemented by the statement that not all the eggs behaved 

 like those drawn. The majority of parthenogenetic eggs 

 never showed any higher degree of differentiation during 

 their development than those drawn in Fig. 157 ; many eggs 

 even remained spherical. The number of trochophores was 

 always considerably larger than the number of eggs that 

 became amoeboid. The majority of parthenogenetic trocho- 

 phores are perfectly spherical. I have often wondered 



