METHOD OF RECORDING EGG DEVELOPMENT. 193 



two processes of cell division resulting in the extrusion of the polar 

 bodies, it unites with the male nucleus derived from the spermatozoon, 

 which in the meantime has entered the egg through the micropyle, has 

 become embedded in the germ disk, and has separated into a nucleus 

 and its accompanying aster. The union of these two nuclei and the 

 formation of an aster inaugurate the process of segmentation. All 

 these processes are microscopic, and not even a suggestion of what is 

 taking place could be inferred from the external appearance. 



These sketches are intended simply to give an idea of what can be 

 seen with the unaided eye during the tender stage ; and as landmarks 

 showing progress in that stage it is hoped that they may be of some 

 practical value. They show stages in the growth of summer-run 

 qjiinnat-salmon eggs with the water at a mean temperature of 57° F. 

 Sketches were made daily, and the age of the stage in temperature 

 units was noted. As the water grew colder, it was noticed that while 

 it sometimes took several days longer to reach a certain stage, yet 

 the number of temperature units was always, within narrow limits, 

 the same for a given stage. This uniformity of results at the given 

 stages is the feature of the system that seems most strongly to recom- 

 mend it for general use, and while different stations, with their differ- 

 ing conditions of water and weather, may produce slightly different 

 results, still, as the conditions at any one station, year in and year 

 out, are the same, the resultant differential will be the same. 



Fig. 1 represents the egg about 1^ hours after impregnation and 

 shows the concentration of minute vesicles at the pole ; also their gen- 

 eral distribution over the entire surface of the egg. They are quite 

 sparsely scattered, however, and soon draw up into the upper third of 

 the egg. A bluish translucent substance occupies the upper quarter 

 of the eggy always rising to the top as the egg is turned. As no 

 microscopic work was done at this time, this substance can not be 

 positively named, but it is believed to be the germ disk attached to 

 the inner egg or yolk mass, the whole inner egg turning with the disk. 

 The eggs are extremely slippery when young. This quality is retained 

 until they enter the tender stage, but is lost before they emerge from it. 



Fig. 2 represents the egg 1 day old at a meair water- temperature of 

 57° F., or at an age of 25 t. u. It shows a distinct '* nucleus" sur- 

 rounded by a clouded band of very minute vesicles. The width of 

 this band is about equal to the diameter of the nucleus. Around it 

 are vesicles which extend down to about one- third the depth of the egg. 



Fig. 3 is very similar to Fig. 2, the nucleus and band being larger. 

 It represents 2 days' growth at the same water-temperature, or an 

 age of 50 t. u. 



Fig. 4 shows a partial clearing up of the clouded band; also a dimi- 

 nution in the size of the central nucleus. Age, 3 days at 57° F. mean 

 temperature, or 7b t. u. 



F. C. 1900—13. 



