174 HENRY J. FRY. 



In the present investigation 1 689 enucleated eggs of Echi- 

 namchnius inseminated by Arbacia sperm produced forty-six 

 blastulae. Since the embryos died at about twelve hours, before 

 maternal and paternal characteristics could be distinguished, a 

 critical analysis concerning nuclear and cytoplasmic inheritance 

 was not secured. Certain observations were made, however, a 

 report of which may be of value to future investigations. 



Dry eggs freshly obtained from the gonopores (Just, '19) do 

 not give a higher percentage of activation, after enucleation, 

 than eggs freshly obtained from the surface of the ovaries. 



Eggs were enucleated one at a time by a glass needle held in 

 the hand (Fry, '24). The cutting is done on an ordinary micro- 

 scope slide placed on the stage of a dissecting microscope. This 

 permits more rapid enucleation than can be accomplished with 

 the machine as about twenty eggs can be enucleated in ten 

 minutes. Hence it is possible to experiment with relatively 

 large numbers of enucleated eggs rather than with several at a 

 time, thus increasing the chance of securing a significant result. 

 That the method gives sure and certain enucleation was shown 

 in an earlier study (Fry, '25). 



Enucleated eggs of Echinarachnius are viable only when frag- 

 mented at temperatures between 15 C. and 20 C. If the 

 cutting is performed at temperatures either below 15 C. or 

 above 20 C., there is practically no activation. The microscope 

 is placed in a box having a glass top through which the oculars 

 project. Openings in the front permit the entrance of the hands. 

 The temperature is roughly controlled by ice containers. Since 

 the air within the box is thoroughly moist, thi? reduces evaporation 

 from the drop of water on the slide that contains the eggs and 

 fragments. Thus changes in osmotic pressure are reduced to a 

 minimum. 



No effort was made to locate the micropyle by the use of inks 

 and the eggs were cut by chance in any plane. Therefore, no 

 data were secured as to the relation between cutting in different 

 planes and the resultant effects upon the development of enucle- 

 ated fragments. 



1 The experiments were carried on at the Marine Biological Laboratory at 

 Woods Hole, Massachusetts, during June and July 1926. 



