LYCASTIS QUADRATICEPS. 



375 



Where one or more ripe ova occupy a somite they usually lie 

 in contact with the digestive tube and are plainly visible as golden- 

 yellow masses, shining through the body-wall (Figs. I and 2). 



The sperm-cells, which are invariably in clusters, are only a 

 little less obvious than the eggs (Fig. 2). They are present in 

 the same somites as the ova and in many others where no ova 

 have been found. The relations in this respect are best seen in 

 tabular form. 1 



Inspection of the table shows that there is no fixed relation 

 between the number of the somites and the length of the speci- 

 men, which of course has its obvious explanation in the differing 

 degrees of contraction which the worms underwent in fixation. 

 Nor is there a fixed relation between the total number of somites 

 and the number of ovigerous somites, or number of ova ; nor 

 between the number of somites and the spermatogenous somites. 

 Thus, between Nos. 5 and 6 there is a disparity of only 13 in the 

 number of somites, but a difference of 21 in the number of their 

 ovigerous, and of 7 in their spermatogenous, somites. The 

 greatest disparity of all, 29, occurs in the total number of ova. 

 Or, stated in percentages, No. 5 has about 22.4 per cent, more 

 somites than No. 6, and 16.66 per cent, more of them produce 

 spermatozoa ; but on the other hand, No. 5 has developed over 322 

 per cent, more ova than No. 6 ! There is really more difference in 

 size, however, than the difference in the number of the somites 

 would indicate, amounting to 41.3 per cent, in the one dimension 



x The counts have been made from entire specimens, usually unstained, mounted in 

 balsam. With a species so small such preparations generally permit internal struc- 

 tures to be seen with admirable clearness ; yet undoubtedly a few small immature ova 

 were overlooked. 



2 Immature. Most of the ova very small, and sperm-cells sot detected with cer- 

 tainty. 



