108 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
produce a new cuticle which has a certain degree of elasticity. My material was insuf- 
ficient to trace with certainty the origin of the reticulated tissue which soon appears 
under the new skin. 
A minute papilla grows out, having the general structure shown in fig. 173. It is 
a spongy network of fibers, containing the potential elements of muscles, nerves, con- 
nective tissue, and blood vessels. Blood flows in an irregular system of large and 
small sinuses. The epidermis of the new skin, which is relatively much thinner than 
the old, is composed of a single stratum of very tall, slender cells, the chitinogenous 
epithelium, and of an elastic cuticula. The epidermis of the papilla is thus structurally 
similar to that which covers all parts of the body when a new shell is being formed 
under the* old. (See p. 77.) 
As the papilla grows out the fibrous tissue becomes gradually differentiated into 
the muscles, blood vessels, and nerves (fig. 172), as in an embryo, and constrictions in the 
cuticle arise, which mark with absolute precision the limitation of the future joints. 
The cuticle at this stage appears to be destitute of hairs, but it contains pores. In 
the stump at the base of the appendage a great mass of large oval bodies is seen. 
These appear as thin solid discs, and when compressed break like starch grains (fig. 
121, pi. 36). They represent connective tissue cells in a certain stage of metamorphosis, 
and in all probability contain glycogen, which furnishes material for the growth of the 
epidermis — that is, of the chitinogenous cells and the shell which they secrete. (See 
78.) They seem to be the same structures which Leydig has described in the 
integument of crabs, under the name of lime concretions (Kalkconcrem elite), and 
which Hoeck calls “Krystall Plattclien” {121-122). Mayer {137) has also figured and 
described what are probably similar bodies in the indurated shell of certain swellings 
which are found in the large claws of the male Heterograpsus lucasii. These he desig- 
nates as “ amyl-like ehitiuous inclusions.” 
In the lobster these bodies stain very diffusely, and sometimes a central figure, 
possibly the impression or remains of the original nucleus, may be detected. The 
histogenesis of these structures and the changes which they undergo have apparently 
never been studied. Their origin is clearly demonstrated by fig. 122, plate 36, from 
a preparation of the maxilliped. It is evident that the large granular mass is the 
product of the parent mesoblastic cell, the protoplasm of which is reduced to a thin 
enveloping shell. 
Fig. 169 represents one of a series of sections cut in a longitudinal plane through 
the first three joints of the right large cheliped of the lobster (sixth stage, length 18 
mm.), the history of which has been already given (p. 105). The appendage of this 
larva had been cut off July 28, and had grown to nearly its full size by August 17, 
when the animal was preserved. Since autotomy occurs in the very young animal as 
well as in the adult, we should be able to determine from this specimen whether 
there is any preformed organ or store of embryonic cells for the supply of the new 
limb at this time. The examination of serial sections through this part of the limb 
reveals nothing but normal tissue cells. Embryonic cells may be present but are 
not discernible. The opening between the basipodite and ischiopodite is reduced to 
a narrow passage by the ingrowth of cuticular cells, to form ectodermic pillars like 
those seen in the carapace of the embryo. The several tissues are bathed in blood, 
which is here confined to no definite channels. Some circumscription of the passage 
leading from the second to the third joint is thus necessary. 
