324 PROCEEDINGS OF THE ACADEMY OF [July, 



and place the capsule containing the eggs in the jelly in 20 per cent, 

 formalin for an hour or two, and then shake the eggs out of the jelly 

 into a mixture of 20 per cent, formalin and 70 per cent, alcohol, equal 

 parts, afterwards transferring them to 80 per cent, alcohol. Unfor- 

 tunately this method leaves shreds of the jelly adhering to the eggs, and 

 as these shreds stain intensely they interfere with the study of the 

 eggs, which are to be stained and mounted entire. To preserve eggs 

 entirely free from the jelly I have found it advisable to slit open the 

 jelly and allow the eggs to drop out into a tall jar of 20 per cent, forma- 

 lin, or into a mixtiu-e of pure formalin (40 per cent.) and a saturated 

 solution of corrosive sublimate, equal parts. If the jar is quite tall 

 (at least eighteen inches) the eggs may be sufficiently hardened before 

 they reach the bottom to preserve their spherical shape, especially if 

 there is a layer of absorbent cotton at the bottom of the jar. After a 

 preliminary hardening in this fluid the eggs may be transferred to 

 other fixing fluids or to alcohol. These eggs were then stained in 

 dilute Delafield's hsematoxylin, and were mounted entire in the manner 

 described by me (1897, 1902) for other kinds of eggs. 



II. Cleavage. 



1: THE UNSEGMENTED EGG. 



I have made no attempt to study the phenomena of maturation and 

 fertilization in these eggs since they are particularly unfavorable for 

 such work, owing to the difficulties of fixation, already referred to, and 

 to the great quantity of yolk, which make the eggs difficult to section. 



The most striking feature of the unsegmented egg is the extremely 

 small ciuantity of the nuclear and cytoplasmic material as contrasted 

 with the yolk. The area of cytoplasm and the nuclear spindle shown 

 in Plate XXIII, fig. 1, are but little larger than in the egg of Crepidida, 

 though the entire egg of Fulgur is about 2,000 times the volume of the 

 egg of Crepidula. The great increase in the size of the egg of Fulgur 

 as compared with that of Crepidula is due almost exclusively to the 

 '.increased quantity of the yolk. 



2. FIRST AND SECOND CLEAVAGES. 



It is one of the surprises connected with the development of this 

 .egg that although the yolk is so abundant the cleavage is yet holo- 

 blastic. When this work was first begun I had thought that the 

 -cleavage in this egg, which is larger than the eggs of many cephalopods, 

 might show some resemblances to the meroblastic cleavage of the 

 ^cephalopod egg. However, this is not the case, for the cleavages, at 



