920 Caroline McGij.i-, 



b) The Growth- A rea in Anax Junius. 



Fig. 40 is drawn iVom a hjngitudinal section of the g-rowth-area 

 iu Anax and shows ahnost all the details of transformation. At a 

 in this figure, the cells are just separating from the germinal mass. 

 A cross-section just a little in front of this point is shown in Fig. 44. 

 and here it would be impossible to tell the ova of Anax from those 

 of Plathemis. The cells have the same darkly staining granular 

 protoplasm, with yolk-nuclei just beginning to be deposited outside 

 the nuclear membrane. The nuclei are large, with conspicuous double 

 nucleoli (Fig. 49, 51, etc.), the formation of which has already been 

 ■described. The inner oxyphile mass represents the primary nucleolus, 

 the outer basiphile substance surrounding it comprises practically 

 all the chromatin in the egg. A delicate linin reticulum permeates 

 the nucleus. 



The great increase in the size of the cells during growth will 

 be seen clearly if Fig. 50, which is drawn from a cell close to the 

 germinal area, be compared with Fig. 60 taken from near the 

 oviduct. 



Fig. ()4 is drawn from a living cell studied in normal salt- 

 solution; it shows well all the details of cell-structure except the 

 linin and cytoplasmic reticula. The alveolar structure of the yolk- 

 granules is very noticeable. 



(a) The Nucleoli. 



In this form during growth, the nucleoli behave very differently 

 from those described in Plathemis. Each ovum possesses one and 

 only one oxyphile nucleolus, which in early growth is either 

 surrounded by the basiphile body ( Fig. 49) or lies by the side of it 

 (Fig. 51 and 52). This nucleolus persists throughout the entire 

 growth period and never dissolves in the nuclear sap. It increases 

 very little in size during growth, and is apparently an unimportant 

 factor in metabolism. The basiphile nucleolus soon separates 

 fi'om the oxyphile (Fig. 52—64) and begins to break up into a very 

 heavy granular spireme which becomes looser as growth proceeds; 

 Fig. 52 shows it just beginning to unwind. In Fig. 53 and 54 it 

 is looser, and so on down the series of drawings. As late as Fig. 58. 

 all the chromatin except a thin layer just inside the nuclear mem- 

 brane, is in this coiled spireme. Eventually, when it is well uncoiled, 

 granules of chromatin begin t(^ break away from its surface, passing 



