NATURAL HISTORY OF AMERICAN LOBSTER. 
289 
Turning to the male and confining our attention for the moment to external anatomy, 
we find correlative structures of great interest. The seminal ducts open to the outside 
much as do the oviducts, but on the basal segments of the last pair of walking legs. 
The openings face the middle line obliquely and are directed backward and downward. 
The underside of the tail is armed with a median row of four sharp spurs, which project 
downward and backward from the sternal bars of the second to fifth abdominal somites; 
in the mature female these protective spines are rudimentary, a condition which certainly 
favors the safe storage and carriage of eggs. 
In place of the seminal receptacle we find in the male small corresponding wing- 
like processes diverging to form a deep V-shaped groove in which rest the tips of the 
stylets or modified first pair of swimmerets (fig. 5, pi. xlhi and fig. 1, a, pi. xxxix). 
The inner branch of the second pair of pleopods bears a peculiar short spur, and it is 
to be noticed that when the swimmerets of the male are directed forward the stylets 
meet on midline between the wings of the sterna just mentioned to form an imperfect 
archway or covered passage, while in the divergent angle behind rest the short hairy 
spurs. That these parts are concerned in the passage of the spermatophores to the 
seminal receptacle of the female can hardly be doubted. Their structure and function 
will be more fully considered after the several organs themselves have been examined. 
THE RIPE OVARY. 
The ovaries, or “coral” as they are sometimes called, are immediately exposed 
upon opening the dorsal body wall. They consist of two cylindrical rods of tissue 
united by a transverse bridge, behind which each lobe gives off a short, straight duct (fig. 
1 , pi. xliv). The ovarian lobes traverse about two-thirds the length of the body, extend- 
ing from the forward end of the stomach to the third, fourth, or fifth segments of the 
tail, and when approaching maturity are of a rich dark-green color. The ripe ovaries 
are so much swollen that they fill all the available space in the upper parts of the body. 
The bead-like eggs are clearly seen through the thin ovarian wall, and when this is 
cut they flow out, if perfectly ripe, in an uninterrupted stream. When the congested 
ovary is not mature the loosened eggs stick together and can not be easily disengaged 
without injury. A female with eggs approaching maturity can be readily distinguished 
by extending the translucent membrane between the tail and carapace, through which 
the color of the ovary is at once apparent, but since the eggs can not be pressed from 
the unyielding body of the animal, there is no way of telling when these are ripe short 
of actual dissection. 
During the long period of growth, which leads up to the production of the first 
generation of eggs, various changes ensue, which are essentially uniform except for 
variations in color imparted by the yolk to the immature ova. After the first generation 
of eggs is expelled a normal reproductive rhythm is established, and during each 
cycle which follows, from egg laying to egg laying, the ovary undergoes a definite series 
of changes, unless the normal rhythms are disturbed by unusual and unfavorable 
conditions. A complete change in environment may necessitate a change in repro- 
48299° — Bull. 29 — 11 19 
