320 



The chromatin of the nuclei of the red cells of Amblystoma (fig. 7) 

 is very abundant, and is disposed in the form of dense angular blocks 

 which are so numerous that little space remains between them. Neigh- 

 boring chromatin masses are connected together by means of several 

 fine short chromatin threads. On account of the great quantity of 

 chromatin the nucleus appears dense and pyknotic, although not 

 absolutely homogeneous in structure. It is very irregular in outline 

 and has many small lobules on its surface. The lobules, which are 

 small and rounded, are produced by numerous grooves and irregular 

 depressions and elevations which run over the surface of the nucleus. 

 In nearly every nucleus one or more of these furrows will cut into the 

 surface so deeply as to produce distinct incisures which divide the 

 nucleus into two or more large lobes. Each of the larger lobes is further 

 subdivided into smaller rounded lobules. This gives the nucleus an 

 extremely irregular outline. 



Small lobules, and occasionally larger ones, are cut off from the 

 nucleus and become isolated in the cytoplasm where they undergo 

 degeneration. In some of the specimens nearly every erythrocyte 

 contains these degenerating fragments in its cytoplasm. 



The erythrocyte nucleus of the garter snake (Thamnophis sirtalis 

 and T. radix) is not as pyknotic as that of Amblystoma, and a rather 

 distinct chromatin network is quite evident. There is relatively much 

 less chromatin present and its arrangement is not nearly so regular. 

 The numerous small rounded lobules and the incisures of the Am- 

 blystoma nucleus are not seen in the garter snake (fig. 8), but long 

 slender pseudopodium-like lobules with swollen, rounded ends are 

 frequent. For this reason the isolated nuclear fragments, when they 

 have first been cut off from the main body of the nucleus, are larger 

 in the garter snake than in Amblystoma. They also undergo degene- 

 ration in the cytoplasm. 



These facts show that the "sauroid" nucleus is not necessarily 

 more pyknotic or degenerate than that of the erythrocytes of the Ichthy- 

 opsidae. The differences in nuclear structure described by Minot in 

 the two groups of vertebrates may be true enough in most cases, but 

 they are certainly not to be found in all of the Ichthyopsidae and 

 Sauropsidae.i) For this reason it seems very unlikely that many 



1) Maximow has also called attention to this fact in the discussion of 

 a paper presented by Minot at the 24th meeting of the Anatomische Gesell- 

 schaft. 



