THE AMERICAN LOBSTER. 
127 
off from the rest of the cells. It should be remarked, however, that in two or three 
days after ovulation (external eggs with segmented yolk) there is a striking lack of 
uniformity in «he condition of the glands, in many the central zymogen zone being 
entirely absent. This may be due to the fact either that some of the glands recover 
from exhaustion raster than others, or that they secrete unequally, or that some are 
not roused to activity at all. 
Fig. 210, plate 49, is from the swimmeret of a female which had probably recently 
hatched a brood and was close upon the point of shedding. As may be seen, the 
glands are much shrunken in size, the cells transparent and non-grauular, as if they 
were completely exhausted. This seems to be a perfectly normal case, but whether 
it has any significance in respect to the molt I am not able to say. 
HISTORICAL SKETCH OF THE CEMENT GLANDS. 
Cement glands have been described in numerous species of macrurous Crustacea, 
but their structure seems to have been imperfectly made out. 
Cavolini, 1 according to Cano (32), maintained that the cement came from the 
oviduct, and Bathke (160) regarded the genital organs as the probable source of this 
secretion. Erdl (62), in 1843, described three membranes in the egg of the lobster, 
and considered the outermost of these to be the secreted product of the oviduct. 
Lereboullet (120) barely escaped the discovery of the cement glands of the crayfish 
in I860, but correctly stated that the cement substance came from beneath the skin 
of the under side of the abdomen. He had indeed communicated this discovery to the 
Natural History Society of Strasbourg in 1852 (published in a note in L’Institut, 
in 1853. See ref. 120.) As he says, zoologists had up to this time been almost mute 
upon this subject, some explaining the attachment of the ova to an extension of the 
primary egg membrane, others, like Milne Edwards (58), to an albuminous secretion 
from the epithelium of the oviduct. Lereboullet described a milky-wliite matter rich 
in fat and nuclei, which is present in the epimeral regions of the abdomen of the 
female crayfish at the time of oviposition, but is not found in the male at any period 
of the year. He supposed that this substance oozed through pores in the cuticle, 
coagulated in the water after fixing the eggs, and that all trace of it subsequently 
disappeared until the next reproductive period. 
The true source of this secretion was first recognized by Braun (22), who, in 
1875, described cement glands in the crayfish. He showed that they consisted of 
clusters of cells, which open to the surface of the abdominal appendages by narrow 
ducts penetrating the cuticle — a single duct to each cluster. A little later (23) he 
figured and described these glands in the six species of decapods. Similar structures 
were found in the carapace and oesophagus. (Esophageal glands (Speicheldrusen) had 
been already seen in several species of crabs, such as Grapsus and JEriphia spinifrons , 
and analogous structures were found in the labrum and maxilhe. 
Vitzou, whose work was published in 1882 (197), found glands generally present in 
the oesophagus of all the Crustacea examined, and they appear in many of his drawings, 
but no attempt seems to have been made to study their histology. The oesophageal 
glands were extremely abundant in the lobster and Palinurus. The ducts are said to 
1 Memoria sulla generazione del pesci e dei granchi. Napoli, 1787. I have not had access to this 
work, and quote it upon the authority of Cano. 
