369 



Table 8. 





Time. 



FUNDULUS X FUNUULUS. 



FuNDULtTS X SQUETE'RIE. 



3.40 p. M. 



July 17. 



Fertilization. 



Fertilization. 



5.50 P. M. 



July 17. 



2 cells. 



2 cells. 



6.35 P. M. 



July 17. 



4 cells. 



4 cells. 



7.25 p. M. 



July 17. 



8 cells. 



8 cells. 



7.45 p. M. 



July 17. 



Begin. 16 cells. 



Begin. 16 cells. 



8.10 A. M. 



July 18. 



Late cleavage. 



Late cleavage. 



12.20 p. M. 



July IS. 



Begin, germ ring. 



Begin, germ ring. 



7.00 P. M. 



July 18. 



1 over yolk. 



Germ ring; J to i over. 



8.15 A. M. 



July 19. 



Blast, closed; optic ve.-^icles 



Blast, closed; optic vesicles poorly 







plainly formed. 



formed notocord; somites. Be- 

 hind normals. 



2.15 p. M. 



July 19. 



Optic vesicles and lens; brown 



Optic vesicles showing; behind 







parts showing. 



normals. 







Hatched. 



No further along. 



The embryos may coiitiuue their developmeiit to a stage where the eyes, 

 heart, ear vesicles, tail, etc., are more or less well formed. At this stage 

 they remain alive until about the time that the normals hatch. 



None of the embryos are formed even approximately normal. The indi- 

 vidual differences are so great that a description of different forms would 

 be of no avail. A brief description of one of the poorer embryos is as 

 follows : The embryo may' form a mere mass of cells so far as external 

 appearances go. This embryo becomes pigmented with many pigment cells 

 which are highly branched. It is bilaterally symmetrical in form, but the 

 distribution of the pigment cells only slightly indicates this. In this em- 

 bryo there was no definitely differentiated heart, but beneath and about one- 

 third the distance back from the anterior end, a mass of cells could be seen 

 regularly pulsating. Just above the heart-mass a vesicle occurred which 

 I take to be the ear. There was no indication of a tail. I repeatedly ob- 

 served the embryo bend itself from side to side so that there were prob- 

 ably muscle tissues formed on both sides. This particular embryo died nine 

 days after fertilization. 



One of the best formed embryos may now be described. Two eyes are 

 formed, although much too small, poorly pigmented, without a lens and set 

 into the anterior surface. Extending out on either side is a large vesicle 

 which is probably an hj-pertrophied ear vesicle. A pretty well developed 



[24—26988] 



