Tl8 THE AMERICAN NATURALIST. [Vol. XXXV I II. 



plcted and the blastopore was about to be formed. These two, 

 eompelled on June 27 to make a journey with me to Maine, in 

 spite of the utmost care, did not survive the hardships of travel 

 and the experiment came to an end. I am thus able to record 

 the development only during the first three days of existence, 

 lea\ in<; the period from the fourth to the eleventh still unknown 

 sa\ e throu-^h analogy with allied forms, and waiting to be written 

 when occasion may offer. 



This early history includes only surface study, mainly of 

 preserv ed material, but seems to be of especial importance as 

 showing a genuine holoblastic type of cleavage when from the 

 later torni of the embryo a meroblastic form was to have been 



Hie various cleavage stages are represented in Fig. i, in 

 which the first perpendicular column represents them as seen 

 troin tile upper pole, the second from the side, and the third 

 troni below; the figures in each horizontal row representing 

 sex eral views of the .same egg. Of these stages the first five 

 occ urred simultaneously at the time the eggs were found, i .00 

 1'. M. June 22. and as no eggs were found the day before, they 

 probably represent stages of 6-15 hours, resulting from eggs 

 hud at intervals during the preceding night. 



The successive changes and the descent of the various cells 

 >eeni exident. and may be traced with an approximate certainty 

 as tar as the 2 ^cell stage, as indicated by the lettering. In the 

 tust stage shown, the first cleavage is complete, separating the 

 e-g into its two halves. A+B + C + D and E + F + G + H, while 

 the second cleavage, beginning at the upper pole, has proceeded 

 nearly to the ecjuator and is separating the halves into the com- 



: in the eggs examined, is not the 



night be expected, but consists of 

 which start near the upper pole as 



ni one of the two former cleavage 

 Similar fissures were observed in 

 pole and it is evident that those 



'clow meet one another, and result 



