44 Papers from the Marine Biological Laboratory at Tortugas. 



34, 56). At the periphery of the egg is a coarsely granular area one or 

 several granules in depth (figs. 38, 39). With iron hematoxylin and orange 

 G the granules stain deep black like chromatin or yolk granules. They are 

 undoubtedly the latter. After a fertilization membrane has been formed 

 these peripheral granules have disappeared, nor are they again to be seen 

 in the blastomeres of the segmentation stages. It is probable that this 

 granular layer contributed to the formation of the fertilization membrane 

 and so disappeared when this was fully separated off. If this view is cor- 

 rect the fertilization membrane is the egg-membrane thickened by the con- 

 tribution from the yolk-granules and as such separated from the ovum. 



Particularly after fixation with sublimate acetic and picro-aceto-sulphuric 

 is the close similarity between the cytoplasm in the living and fixed condition 

 (but for increased definiteness in the latter case, amounting to an identity) 

 very striking. It exhibits a structure of larger and smaller alveoli about 

 whose walls are ranged in single line the minute granules or microsomes 

 as already described by Wilson and here and there throughout the network 

 large granules, probably yolk, similar in size to the peripheral granules. 

 The faithfulness of preservation as observed in the cytoreticulum leaves 

 little room for doubt that also what is seen in regard to the nuclear retic- 

 ulum, the maturation mitoses, and particularly the dissolution of the nucleo- 

 lus, are true representations of what actually occurred in the living egg. 

 Atypical stages (fig. 56) can, therefore, in no case be regarded as artifacts 

 due to faulty fixation, but must be interpreted as the result of abnormal 

 development or degeneration processes. 



The living egg shows a nucleus with an extremely delicate meshwork 

 spun through a homogeneous ground-substance. Owing to the presence of 

 a large amount of nuclear sap, the fixed nucleus differs greatly from that 

 of the living egg. The reticulum now appears coarse and wide-meshed 

 (figs. 29, 38, 39). It forms a dense basket-work about the nucleolus. 

 After staining with iron hematoxylin and orange G, when the hematoxylin 

 is greatly withdrawn the reticnlum is uniformly yellow ; when the stain is 

 only slightly extracted chromatic swellings appear along the reticulum, 

 giving it a beaded structure, and larger dark-staining masses (karyosomes) 

 are seen at the intersections of the meshes (fig. 39). Auerbach's stain 

 shows no sucB difference, but leaves the entire network uniformly red. 

 Thus again it becomes evident that in the linin of the reticulum are areas 

 which in degree of metamorphosis or condensation represent a transition 

 stage between linin and chromatin. 



The nucleolus yielded different appearances according to the stains that 

 were employed and the length of their application. With the iron hema- 

 toxylin and orange G combination the oocyte at the height of the growth- 

 period exhibits a nucleolus extremely tenacious of the hematoxylin stain. 

 An amount of extraction which renders the cytoplasm and nuclear retic- 



