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ever to turn out in a uniform manner, and eventually led me to 

 distrust these conclusions. In the effort to get a definite point on the 

 egg surface, from which to measure the movement of the blastopore 

 lip, I was led to adopt the following method — which, in plan, is 

 essentially like that used by Eycleshymer ('95) in his studies 

 on Am bly stoma. The egg, which had been naturally or artificially 

 fertilized, was allowed to develop under normal conditions, until 

 the dorsal lip had just made its appearance or was about to do so. 

 It was then compressed , after the well knowii fashion , between 

 glass slides, separated at first only by wax feet (so as to graduate 

 the compression), eventually by wooden wedges. The slides were 

 bound together wdth rubber bands, turned so as to bring the white 

 pole of the egg up, and placed in a shallow dish of w^ater on the 

 microscope stage. A strong light with bulls-eye condenser, Zeiss A or 

 similar (^/g inch) objective, and a 2 micrometer eye-piece, were used. 

 With this combination, the individual cells of the surface, both the 

 pigmented and the yolk cells, could be seen with distinctness, and 

 the changes of shape, size, coloration, and position, which they under- 

 went, could l^e accurately follow^ed. Such eggs resulted in the form- 

 ation of embryos with well developed neural folds, and which 

 seemed to be normal in every respect, save for their compressed 

 shape. Although there is a strong presumption that the cell move- 

 ments observed in the inverted eggs are those which occur in the 

 normally situated egg, I must for the present leave this an open 

 question. With the help of an inverted microscope, which enables 

 the under pole of the egg, kept in its normal position, to be studied, 

 I have verified my observations on the occurrence of delamination in 

 the inverted eggs, and hope in the future to study the cell move- 

 ments. 



The eggs of Chorophilus vary in diameter from 1,25 mm to 

 1,5 mm. All the eggs in a mass (collected) are of the same size ; 

 and where the eggs were artificially fertilized or were obtained from 

 a pair copulating in confinement, all the eggs from a pair were of 

 the same size. The egg is a favorable one for study. The pigment 

 is reddish-brown, but so abundant that the pigmented region, during 

 early stages of development, looks to the eye almost black. With 

 this pigmented region, the clean white yolk is sharply contrasted. 

 As a rule, the larger eggs, of about 1,5 mm diameter, were chosen 

 for observation. In the compression experiments these were com- 

 pressed until they had a diameter of about 2 mm. 



