No. 3] THE EGG OF ALLOLOBOPHORA FOETIDA. 135 



the enlargement of the sap globules. It would seem, rather, 

 that this sap, which in some form must also be present in 

 oocyte first order, is molded into the more definite shapes of 

 the later stages by a rearrangement of 

 the other constituents of the cytoplasm. 

 If an ^^^ is gently pressed until a tiny 

 break is made in the outer membrane, 

 the larger globules become somewhat 

 constricted in form when flowing through 

 this aperture as represented in Text- 

 fig. V. After escaping from the pres- 

 sure of the aperture, they regain their 

 spherical shape. 



When an ^gg at the pronuclear stage 

 has been kept in water too long, the glob- 

 ules fuse and swell, many of them increasing in size two or three 

 times their diameter, givnng the &gg a vacuolated appearance. 



This rapid and definite response to abnormal conditions sug- 

 gested to us their value as a guide to determine the relatively 

 harmful effect of killing fluids, for any fixative producing a 

 marked disturbance of the sap globules or the surrounding 

 substance would probably cause the globules to fuse or break 

 up at once. Our method has been as follows (under a Zeiss 

 2 mm.) : First, to focus on the periphery of an egg showing 



Fig. V. — Sap globules pressed out 

 of living egg. ( Pronuclear stage.) 

 Free-hand sketch. To the right 

 a large globule has broken into 

 several small ones. One of the 

 large globules above is the result 

 of the fusing of two smaller ones. 





B 



Fig. VII. 



Fig. VI. — /}. Sap globules of living egg. B. The same globules after 15 minutes in i per 



cent, osmic. Zeiss 2 mm. immer., oc. 2 (camera). 

 Fig. VII. — ^ . Sap globules of living egg. B. The same area after 15 minutes in chromo- 



acetic. Zeiss 2 mm. immer., oc. 2 (camera). 



pronounced sap globules, sketching about half a dozen of these 

 with the aid of the camera (Text-fig. VI, A) ; second, one of 

 us then applies the fixative, while the other closely watches 

 the effect produced on the sap globules ; third, after 1 5 to 



