DR. NELSON ON THE REPRODUCTION OF THE ASCARIS MYSTAX. 
593 
Fig. 71. 
Fig. 72. 
Fig. 73. 
Fig. 74. 
Fig. 75. 
Fig. 76. 
Fig. 77. 
Fig. 78. 
Fig. 79. 
Fig. 80. 
Fig. 81. 
Fig. 82. 
Fig. 83. 
a. The embryonic vesicle, f. The chorion, k. The embryonic spot. 
m. Clear fluid filling the space between the yolk and the chorion, n. The 
embryonic granules, o. The yolk-membrane become spherical, and en- 
closing the granules. 
An imperfect ovum placed in creosote water, by which the separation of a 
yolk-membrane w^as prevented, and yet the embryonic vesicle divided. 
a. The two divisions of the embryonic vesicle occupying opposite extremi- 
ties of the egg, but without any membranous or granular investment. 
A perfect ovum, in which the embryonic spot has divided, a. The em- 
bryonic vesicle elongated, k. The divisions of the embryonic spot. 
Ovum in which the embryonic vesicle has divided and the protrusion of 
the yolk-membrane commenced, a. The divisions of the embryonic vesicle. 
k. Their embryonic spots, o. The protruded portion of the yolk-mem- 
brane. 
Ovum w'hose yolk presents the hour-glass appearance, a. The embryonic 
vesicles, which by constant gyrations have forced the yolk-membrane into 
an hour-glass shape, o. The yolk-membrane constricted in the middle by 
its own elasticity. 
Ovum, with the yolk divided into two. a. The embryonic vesicles, k. Redivi- 
sions of the embryonic spots, n. The two yolks, o. The divisions of the 
yolk-membrane, caused by the joint operation of its own elasticity and 
the traction of the embryonic vesicles. 
Ovum whose yolk has divided into four. o. The four portions of the yolk. 
Ovum whose yolk has divided into thirty-two. o. The divisions of the yolk. 
Ovum the whole interior of which is filled with the granules formed by 
often-repeated division of the yolk. o. The granules thus formed. 
Ovum in which the embryonic membrane or cuticle of the worm is first 
seen. p. The depressed portion of the membrane, r. The fluid filling 
the interspace between the membrane and the chorion. 
Ovum in which the depression of the embryonic membrane has given a 
cup-like form to the mass of subdivided granules, p. The depressed por- 
tion of the embryonic or cuticular membrane. 
An ovum in which the two sides of the cuticular membrane having united, 
a fleshy ring has been formed, p. The united portion of the cuticular 
membrane. 
An ovum where the fleshy ring begins to present a constriction at one 
point, s. The constriction. 
An ovum in which the head and tail of the worm are visible, o. Untrans- 
formed granules, p. Cuticular membrane covering and giving shape to 
the worm. s. The head and tail of the embryo. 
