154 ETHEL BROWNE HARVEY. 



in a modified Engelmann's chamber. When the eggs are deprived 

 of oxygen at any stage from fertilization to the completion of 

 the first cleavage, development is arrested, but on readmission 

 of air, continues and normal larvae result. 



2. When deprived of oxygen immediately after fertilization, 

 the sperm aster gradually fades out and when air is readmitted, 

 the aster reappears in the same position. 



3. When deprived of oxygen at any later stage up to the 

 metaphase, the astral fibers disappear but reappear on re- 

 admission of oxygen in the same position. Eggs have been as 

 long as three hours without oxygen. 



4. When deprived of oxygen at the full metaphase, the astral 

 fibers disappear but sometimes not till after two hours. When 

 air is admitted, the mitotic figure often appears as a white 

 streak between two elongated astrospheres. Subsequent de- 

 velopment is very irregular, often many asters appearing and 

 cleavage planes dividing off large or small cells and subsequently 

 often becoming obliterated, and other cleavage planes forming. 

 After a while the eggs right themselves, giving rise to regular 

 normal blastulae and larvae. 



5. The egg may elongate and cleavage planes may start to 

 come in at first during lack of oxygen, but the egg rounds out 

 and the division plane is obliterated if kept longer without 

 oxygen. These eggs proceed with irregular cleavages when air 

 is admitted, but result in normal blastulae. 



6. If kept without oxygen at any stage after completion of the 

 first cleavage to the metaphase of the second, normal cleavages 

 result on admission of air. 



7. If kept without oxygen just before second cleavage, when 

 air is admitted, irregular divisions and fusions take place, but 

 normal blastulae result. 



LITERATURE LIST. 

 Demoor, J. 



*95 Contribution a 1'etude de la physiologic de la cellule. Arch. Biol., 13. 

 Hertwig, O., and R. 



'87 Uber den Befruchtungs- und Theilungsvorgange des thierischen Eies unter 



dem Einfluss auserer Agentien. Jen. Zeitschr. N.F. 13. 

 Hertwig, O. 



'90 Experimented Studien am thierischen Ei vor, wahrend und iiach der 

 Befruchtung. Jen. Zeitschr. N.F. 17. 



