Chapter XIII.— THE EMBRYOLOGY OF THE LOBSTER. 
I shall not attempt to give a detailed account of the embryonic history of the 
lobster, although for several seasons I have spent much time both in collecting and 
preparing material for this purpose. I will offer only a few notes on the early 
phases of development, and, to lend continuity to the whole, will sketch briefly the 
changes in external form which the embryo undergoes. 
Early embryologists, Rathke in particular, to whom reference has already been 
made ( 160 ), examined the older embryos of the lobster or dissected them from the 
egg membranes, but the only paper of this period which attempts to deal directly with 
the embryology of the animal is that of Erdl ( 62 ), published in 1843. Erdl treats 
of the laying of the eggs and the fastening of them to the appendages of the 
mother; of the nature of the laid egg and of the external anatomy of the older 
embryos; but his work was done before the modern methods of microscopical research 
had been discovered. This pioneer observer was thus greatly handicapped and his 
results are now of but little value. 
Smith figured and described the external anatomy of a well-advanced embryo from 
a lobster captured May 2, 1872, at New London, Connecticut ( 182 ). This stage nearly 
corresponds to that shown in cut 38. 
In September, 1891, a paper on the Embryology of the Lobster, by Buinpus, 
appeared, in which the early stages, to the close of the egg nauplius period, are care- 
fully described and illustrated by very accurate and beautiful drawings ( 30 ). 
A short account of my earliest studies appeared in 1S90 ( 91 ), and this was followed 
by additional notes in May, 1891 ( 92 ), in 1893 ( 96 ), 1894 ( 97 ), and 1895 ( 100 ). 
NORMAL DEVELOPMENT. 
THE MATURATION AND SEGMENTATION OP THE EGG. 
In the section on the growth of the germinal vesicle I have described the only 
stage in the maturation of the egg which has been directly observed (p. 154, plate 42, fig. 
101), where the germinal vesicle has approached the surface and is undergoing indirect 
division, being overtaken in the metakinetic stage. As already stated, it is evident 
that in this particular egg the germinal vesicle was about to give off a polar body. 
Buinpus, who was the first to detect polar bodies in the egg of the lobster, gives 
the following account of them: 
They are present in many eggs, and appear to be attached at no special point of the vitellus, so 
far as the flattened area is concerned, being sometimes within it and sometimes without. It may be, 
however, that I have only seen them in secondary positions; for in some cases they seemed to move 
freely about within the egg membrane. They were not observed in process of formation, nor were 
they invariably present. Before the blastula is formed they disappear. (30) 
I was unable to satisfy myself that the polar cells could be distinguished with 
certainty, and so have not figured them. It is difficult to detect such minute bodies 
in so large and so opaque an object as the egg of the lobster, and owing to mechanical 
causes, possibly through the emission of the polar bodies themselves, minute spherical 
globules of food yolk are set free and float in the fluid which underlies the eggshell. A 
202 
