870 THE AMERICAN NATURALIST. 
are carefully scrutinized at this period, it will be observed that 
some of them have more cytoplasm than the adjacent cells 
(Fig. 5). These few cells, which I have termed ova centers, 
become mature by the continuous increase of the cytoplasm, 
which is accomplished by the thrusting out of protoplasmic 
processes which surround the adjacent cells 
and absorb them into the developing egg 
(11). The nucleus appears to be in a state 
of degeneration in most of the cells adjacent 
to the egg. Some of the nuclei have their 
membrane only, while others retain all of 
the parts of the nucleus even after they have 
been taken into the egg (Fig. 7). Here 
some cells have just been taken into the main 
mass of cytoplasm. The various stages in 
the degeneration of the nucleus are also evident. Not all of 
the primitive ova are thus consumed; some will be found which 
have not been utilized at all. They have simply remained 
undeveloped and are found scattered among the mature eggs. 
They seem not to serve any purpose in egg formation, but 
represent remnants of undeveloped and unused cells, 
Fic. 7. 
LITERATURE. 
L. AGassiz. Contrib. Nat. Hist. N orth America. 
A. AGAssiz. North American Acalephe. 
F. BRAUN. Biologisches Centralblatt. 1894. 
ALBERT LANG. Biologisches Centralblatt. 1894. 
KORSCHELT AND HEIDER. Invertebrate Embryology. 
LANG. Comparative Anatomy. Pt. i. 
HARGITT AND OSBORN. American Naturalist. January, 1894. 
S. F. Hickson. Quar. Journ. Micr. Sci. Vol. xxxii. 
VARENNE. Les Polypes Hydraires. 
McCRADY. Proc. Elliott Soc. Nat. Hist. Vol. i. 1857. 
DoFLEIN. Die Eibildung bei Tubularia. Zeit. f. wiss. Zool. Bd. lxii, 
p- 61, etc. 
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