NATURAI. 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. xliii and fig. i, 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. 

 I , pi. xuv) . 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- 



