418 T. H. MORGAN. 



and the ovaries are so far from the anterior end. Here more 

 segments might have regenerated than were lost. 



Fortunately we are dealing with an hypothesis that could 

 be tested by experiment. I at once set to work to determine 

 whether or not the same number of segments reappeared when 

 the anterior ends were cut off. I also wished to find out 

 whether a greater number of modifications than in the average 

 worms were thus produced. A later section gives the result 

 of these experiences. 



IV. Study of Embryos. 



Capsules containing embryos of L. foetid us were collected, 

 and the embryos killed immediately on their emergence from 

 the cocoon. Out of 170 embryos there were twenty-five that 

 showed abnormalities in the arrangement of the rings. This 

 is in the proportion of 1 to 5"2. In other words, there are 

 fewer cases of abnormalities in young worms than amongst 

 adults. In the latter the proportion was one to two. 



This apparent contradiction finds its explanation in the fact 

 that the adults are often found regenerating lost metameres, 

 and proportionately the number of abnormalities in these 

 newly formed parts is greater than in the embryos. This will 

 be taken up more fully in another section. 



The number of metameres in the young worms that have 

 just left the capsules depends to some extent, as the following 

 table shows, upon the size of the young worms. The size seems 

 to be in general connected with the number of embryos that 

 develop in the capsule. Amongst the worms in the same 

 capsule, however, there are variations in size, and we can only 

 make some such general statement as this, that where many 

 embryos are present in the same capsule they are each smaller 

 when they leave the cocoon than when fewer embryos are 

 present. 



The following table indicates, in a rough way, the rela- 

 tion between the size of the embryos and the number of 

 metameres : 



