CASTLE : EMBRYOLOGY OF CIOXA INTESTINALIS. 217 



by the different tints of blue which they exhibited. Iron hrematoxyUn 

 was sometimes employed instead of Ehrlich's, but the results were no 

 better — indeed not so good — for the differentiation of organs or their 

 fundaments. 



For studying the processes of maturation and fertilization sections 

 alone could be employed on account of the opacity of the eggs. In mak- 

 ing sections of these stages orientation was of course impossible, so that 

 a large number of the eggs was embedded together, without previous 

 decortication, and cut at random. The egg membranes, so far from 

 being an obstacle, were at these stages a positive advantage, since they 

 served to protect and hold the polar globules in place. The material 

 employed in the study of maturation and fertilization stages was killed 

 either in Perenyi's or in Hermann's fluid, the best results being obtained 

 from the former. For convenience the killing of each day will be referred 

 to as a series (A, B, or C), made up of lots (1, 2, 3, etc.) which were 

 killed at intervals of about ten minutes, the first lot being killed as soon 

 after the laying as a sufficient number of eggs could be collected, usually 

 about five or ten minutes. 



IV. MATURATION AND FERTILIZATION. 



The eggs of series A, lot 1, show an early stage in the process of matu- 

 ration, namely, the formation of the first polar globule. Figure 1 repx'e- 

 sents a section through one of the eggs of this lot most advanced in 

 development. The egg envelopes, which rest close down upon the egg, 

 are left out in this and all the other figures. Already at this stage we 

 recognize that the egg is made up of two unlike hemispheres, one richer 

 in yolk, the other richer in protoplasm. The former occupies the future 

 dorsal or endodermal side of the egg, and at the centre of its sui-face, as 

 stated in my preliminary communication ('94), the polar globules foi-m. 

 The cell division which will give rise to the first polar globule is seen in 

 this figure to be already well advanced, the chromatin being accumulated 

 at the two ends of the spindle. About the deeper end of the spindle there 

 is a small space free from yolk granules and occupied by a finely granular 

 deeply staining mass of protoplasm, of which we shall have more to say. 

 The entire remainder of the dorsal hemisphere, except that small portion 

 of it occupied by the spindle itself, is filled with rounded yolk granules 

 (cf Fig. 2) of a rather uniform size, closely packed together, but with 

 slender films of staining protoplasm passing between and around them. 

 Davidoff's ('89) beautiful figures, particularly his Tafel VI. Fig. 33, 



VOL. XXVII. — NO. 7. 2 



