ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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(2) In the young ovicell a polypido bud is found, which consists of 
a tentacle-shcath, and a part which represents the alimentary canal of a 
polypide. 
(3) With this last one of some small egg-cells present in various 
parts of some of the growing points becomes closely related. 
(4) The alimentary canal grows round the ovum, and becomes a 
compact multinucleated follicle; the egg at first lies in an excentric 
cavity of this follicle. 
(5) The ovum segments, and the blastomeres may, in early stages, be 
completely separated from one another. 
(6) Meanwhile the ovicell is maturing, and soon becomes shifted to 
some distance from the growing point, owing to the superposition of 
new zooecia above it ; its non-calcified aperture becomes constricted, and 
grows out into a long tubular orifice. 
(7) At the end of segmentation the embryo consists of a small mass 
of undifferentiated cells, lying near the distal end of the follicle ; this 
last now forms a spherical knob which projects freely into the interior 
of a spacious tentacle-sheath. 
(8) The follicle becomes vacuolated, and is soon transformed into a 
nucleated protoplasmic reticulum, while the tentacle-sheath loses its 
distinctness. 
(9) The number of blastomeres increases, but, as at all other stages, 
excepting the earliest, cell-limits are indistinguishable. 
(10) The embryo, now considerably increased in size, although re- 
maining a solid mass, without differentiation of organs, grows out into 
several finger-shaped processes, which are generally directed towards 
the distal end of the ovicell. 
(11) The finger-shaped processes are divided up by a series of trans- 
verse constrictions into rounded masses of cells, each of which becomes 
a complete larva. 
(12) This process of embryo-formation continues during the whole 
functional period of the life of the ovicell, and even proceeds actively at a 
stage when many of the embryos are mature or nearly mature. More 
than one hundred (secondary) embryos may be present at any one 
time in one ovicell, and they are all produced by budding from one 
“ primary embryo.” 
(13) Each “ secondary embryo ” acquires its well-known two layered 
condition at the time of its separation from the budding mass of embry- 
onic cells. It developes in a vacuole of the protoplasmic reticulum, 
which presumably nourishes it. 
These facts explain the considerable difference in the structure of 
the Cyclostome larva, as compared with that of other marine Polyzoa ; 
and at the same time explains why it is that no observer has ever suc- 
ceeded in giving an account of any process corresponding to egg-cleavage 
in the Cyclostomata. 
Comparing his results with those obtained by other workers on 
other groups, Mr. Harmer reminds us that in Tunicates, Ccelenterates, as 
well as in Polyzoa, there are remarkable cases of the formation of buds 
from slightly differentiated masses of cells ; and it is in these three 
groups that budding in the adult condition is a more normal event than 
in other groups of animals. In them, it is further to be noted, that, just 
1893. N 
