581 



shape. It is about -0008 in diameter. The macula germinativa is 

 single, and somewhat granular in appearance. 



About the same time as the germinal vesicle, the oil globules make 

 their appearance, and soon become the most conspicuous part of the 

 egg. They are at first very small, but in a mature egg the larger 

 ones are as much as '0016 in diameter. The oil globules may often 

 be seen with their sides much flattened by mutual pressure, and 

 must therefore possess a somewhat compact pellicle. 



Very soon after the appearance of the first oil globules, the egg- 

 follicle loses its pear-shaped form, the basal part swells, and is sepa- 

 rated from the apical part containing the nuclei of the vitelligenous 

 cells, by a constriction. It now perfectly resembles the egg-chamber 

 of any ordinary insect, in consisting of an upper chamber containing 

 the vitelligenous cells, and a lower chamber devoted to the germinal 

 vesicle and the yolk. 



According to M. Leydig, the constriction gradually disappears, 

 and the egg finally occupies both chambers ; but this is incorrect, and 

 M. Leuckart is right in asserting that the vitelligenous cells dis- 

 appear, and the upper chamber becomes atrophied, so that the mature 

 egg lies in the lower chamber only. This process is exactly that 

 which the analogy of other insects would lead us to expect. 



The general cavity of the body of the female Coccus always con- 

 tains an immense number of oval green cells, apparently of a parasitic 

 nature. They are -g-^Vfr * n length, and vary in length, but on an 

 average about 6 3 -. Coccus persicce contains a number of similar 

 bodies, which however are cylindrical. Almost always immediately 

 after the disappearance of the vitelligenous cells, two or three masses 

 of these cells may be found at the lower part of the upper chamber, 

 and soon after in the egg itself. It is difficult to understand why these 

 cells should appear at so definite a period in the history of the egg- 

 formation. Prof. Huxley has pointed out to me that Dr. V. Wittich 

 has already described a Conferva found in hen's eggs. It does not, 

 however, seem clear that these eggs would have arrived at maturity, 

 and I believe that the parasites of Coccus are the first which have ever 

 been known to exist in eggs without impeding their development. 



The mature egg contains numerous vitelline sphaerules which are 

 from -g-^j to -g-^j-Q in diameter, and offer every appearance of true 

 cells, but that they contain no nucleus. 



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