286 PROCEEDINGS OF THE NATIONAL MUSEUM vol. ii4 



more or less directly dorsad to merge with the ental end of the spermi- 

 ducal gland, either more or less abruptly, or by way of an attenuated 

 lobe of the latter organ. Holt (1954) has remarked considerable 

 difference in the diameter of the deferent ducts between C. branchio- 

 phila and C. philadelphica, suggesting that in sectioned material it 

 may be possible to note size differences of taxonomic significance. 



Spermiducal gland. The union of the two deferent ducts brings us 

 to an abruptly larger and more intricate portion of the sperm transfer 

 system. This is a rather plump and heavily glandular organ of very 

 variable size, shape, and proportions, composed internally of a single 

 layer of glandular epitheUum. It is located in all species on one side 

 of segment vi, lying in the coelomic cavity between the gut and body 

 wall and readily visible in well-cleared whole mounts. In all species of 

 Cambarincola, the spermiducal gland is oriented in a distinct]}^ oblique 

 plane across the segment, with the ental end cephaloventrad in loca- 

 tion, and the ectal end caudodorsal. In contracted specimens the 

 orientation may be dorsoventral; eversion of the bursa tends to draw 

 the ectal end ventrad, bending the gland into a C shape or alining it 

 horizontally. 



The precise function of the spermiducal gland remains in some 

 doubt, although from its histological character we can assume it 

 contributes some material beneficial to the passage of spermatozoa or 

 to the accomplishment of sperm transfer. Anatomically, it is to be 

 considered a speciahzed section of the deferent ducts both prior to, 

 and ectad of tiieir commissure into a single conduit. In some genera, 

 such as Branchiohdella, the deferent ducts enter into the gland quite 

 near its ectal end, with the main bulk of the organ greatly prolonged 

 entally and variously coiled in the coelom. In Cambarincola and its 

 related genera, the gland is basically Y or T shaped, the ental branches 

 forming the places of entry of the deferent ducts, and this arrangement, 

 from a morphological standpoint, is probably a reflection of the 

 primitive form in early branchiobdelhds. Departure from this 

 arrangement seems to occur chiefly in the genera which are concom- 

 itantly speciahzed in other respects as well; in the spermiducal gland 

 we have, therefore, a useful sort of yardstick for gaging affinities. 



Assuming that a Y-shaped gland is a generalized condition, we can 

 likewise essay an arrangement of the species of Cambarincola into 

 groups or series of progressive speciahzation, culminating with the 

 gland taking a simple tubular form with little or no lobing at the 

 entry of the deferent ducts so that the Y shape is essentially lost. 

 This morphological progression is one frequently employed in the 

 following classification of the genus. T\Tien the entry of the ducts 

 is marked by an acuminate production of the gland, so that the 

 transition is a gi-adual one, the gland is regarded as "lobed" and the 



