No. 2.] ANURIDA MARITIMA. Pigg | 
yolkless alimentary canal and the remaining viscera. Mordivilko 
(95), discussing the structure and development of some of the 
aphides, speaks of Metschnikoff’s “‘ secondary yolk ” (Metschni- 
koff, 66), and shows how it lies in the body cavity surrounding 
the reproductive organs and causing a wonderfully rapid growth 
on their part. Among the vertebrates certain forms exist in 
which a quantity of the embryonic yolk is associated with the 
germ cells, causing their rapid growth. Petromyzon, the lam- 
prey, belongs in this category, and, as shown in Fig. 66, much 
of the yolk is included among the germ cells.} 
Summary. 
Summing up the results of this investigation on Anurida the 
following points are of interest: 
(1) That the ovary is very simple in character, no arrange- 
ment corresponding to the ovariole of the higher hexapods 
being present. 
(2) A long anterior elongation is present, composed of cells 
non-germinal in character and serving as a suspensory ligament. 
Homology with the “‘ Endfaden ” is uncertain. 
(3) Ova are associated with nutritive cells that show distinct 
“yolk nuclei” at a certain stage. 
(4) The germinal vesicle early becomes invisible and the 
nucleus does not again appear until after the polar bodies are 
given off. 
(5) The egg is spherical, cleavage holoblastic at first and 
slightly unequal. 
(6) There is a multipolar immigration suggesting gastrulation. 
(7) Outer and middle germ layers are formed by migration, 
the entoderm remaining behind in the yolk with yolk cells. 
(8) A precephalic organ homologous with the dorsal organ of 
some crustaceans, and the indusium of Xiphidium is developed 
in the early blastoderm stages. 
(9) There are at least three cuticles formed during preblasto- 
dermic stages; two of the three are crenated. 
1 This figure is from an unpublished drawing of Dr. W. M. Wheeler, who 
kindly lent it for this purpose. 
