DEVELOPMENT OF PARAVORTEX GEMELLIPARA 513 



As to the general arrangement exhibited by this group of 

 melanin spherules, the early irregularity soon gives way to that 

 of a cup whose concavity faces outward (fig. 30 d, e). Conse- 

 quently a meridianal section is crescentic. The floor of the cup, 

 lying against the nucleus, consists of from two to four rows of 

 larger granules, while as the rim is approached the thickness is 

 gradually reduced to one small sphere. 



According to the second type of melanin deposition many 

 minute particles arise simultaneously in the cytoplasm between 

 the eccentrically placed nucleus and the outer membrane of the 

 eye cell. Figure 31 represents the appearance and history of 

 these granules. Since the final arrangement is the same as in 

 the eye at the end of the series described above, it appears either 

 that the spherules nearest the nucleus increase more rapidly 

 in size while those at the margin of the cup remain consistently 

 smaller, or that new granules have subsequently been added to 

 this rim. The latter hypothesis is supported by the fact that a 

 larger number of spheres is present in the definitive eye than 

 was first seen to arise. 



It seems clear that the pigment granules arise in the cytoplasm, 

 probably under the influence of nuclear energy. Their arrange- 

 ment and appearance are not visibly affected by the method of 

 preparation; hence they can be favorably studied in preserved 

 material. When first detected each is a tiny homogeneous 

 refractive body whose form is that usually assumed by a drop 

 of fluid whose surface tension properties are different from those 

 of the fluid in which it is suspended — m this case cytoplasm. 

 There is no evidence that these spherules enlarge by the accretion 

 of successive layers of a more solid material. The conditions 

 rather favor the idea that they grow in the manner observed 

 in the case of fat drops, i.e., by an accumulation of more and 

 more fluid. 



With the increase m size the yellowish color deepens to a 

 reddish brown, and a darker central dot appears in each granule 

 (fig. 30 c) . From this point on there is little to be noted beyond 

 the increasing opacity due to the greater amount of material. 

 Finally, when the pigment spheres have reached their full size 



