THE AMERICAN LOBSTER. 157 



THE OVIDUCT. 



The oviduct is a straight tube of nearly uniform caliber (tigs. 119, 123 od), which 

 opens to the exterior in a hairy papilla on the coxopodite of the third pair of pereio- 

 pods. The skin is folded in the mouth of the opening so as to form a valve which 

 prevents the ingress of water. The appearance of the duct when eggs are passing 

 out is shown in fig. 119. The ovary had collapsed, but these eggs failed of passage. 



The structure of the duet is the same throughout. It has a thin wall of muscular 

 and connective tissue, and a characteristic epithelium of tall columnar cells. The 

 latter undergo so marked a change at the period of ovulation that there can be little 

 doubt that they have some important function to perform. As shown by a comparison 

 of figs. 167, 108, taken respectively from a lobster just before and just after ovulation, 

 these cells become very greatly elongated and vesicular. One would infer that they 

 secrete a liquid which is poured out with the eggs when they are laid. Whether these 

 cells take any share or not in forming the cement I do not know. 



THE SEMINAL RECEPTACLE. 



The sternal pouch of the female was noticed and roughly figured by Nicholls in 

 the Philosophical Transactions of the Eoyal Society for 1731, but he entertained a 

 wrong notion of its function. His interesting and unique account of this organ is as 

 follows (141): 



lirtween the two last legs and the two legs above them there are two processes, which, from their 

 resembling the nyrnphie of women, I shall term nymphajform processes. These processes are covered 

 with hair, and unite at their bases without leaving any passage. The two processes, which 



I have termed nymph;eform, in the female make a more obtuse, angle at the union of their bases, are 

 less hairy, and leave a passage, through which it is probable the ova are emitted, to be affixed to the 

 appendages under the tail. 



This remarkable conclusion reached in the last paragraph is unexplained even by 

 the forced comparisons which were employed. 



The observation of Nicholls was forgotten, and the structure which he imper- 

 fectly described was overlooked until its true function was discovered by Bum pus 

 in 1891 (30). 



The seminal receptacle lies on the under side of the female near the junction of 

 the thorax with the abdomen. (For its position and general appearance see plate 7, in 

 which the median slit is clearly shown, and for details, fig. 130, plate 38.) Its paired 

 wing-like processes, the enlarged sterna of the seventh thoracic segment, are tinged 

 with bright blue and form, with a wedge-like middle piece belonging to the sternum 

 of the eighth thoracic segment, a somewhat heart-shaped body. There is a median 

 slit with elastic edges, and if these are depressed, as Bumpus remarks, a grayish 

 substance, the spermatic fluid, sometimes oozes out. The middle sternal piece is 

 prolonged inside the chamber into a stout keel-shaped body strengthened with thick 

 deposits of chitin, which have a yellowish color and horny consistency. This is sup- 

 ported by a pair of irregular rods belonging to the endopbragmal system, which meet 

 on the middle line. If the molted shell of a lobster is examined, in place of a solid, 

 horny keel, a membranous pouch is found. The solid keel-shaped mass is probably 

 absorbed before a new keel is formed. In the living animal the seminal receptacle is 

 a narrow, irregular cavity. 



