VOL. 114 



292 PROCEEDINGS OF THE NATIONAL MUSEUM 



ture Perhaps it provides some sort of secretion which facihtates 

 longer retention of viable sperm. GeneraUy speakmgm species 

 which have been adjudged conservative or primitive on the basis o 

 other characters, the spermatheca tends to have a long, slender ectal 

 duct and a small, globose ental bulb without an ental process. More 

 specialized species reduce the length of the ectal duct, enlarge the ental 

 bulb, and add a glandular ental process. 



Relationships Within the Family 



So far not enough is known of the branchiobdeUids to permit the 

 formulation of any lasting concepts about the affinities of genera to 

 each other. A major difficulty lies in the fact that heretofore the 

 classification has been based on characters which probably are of little 

 phylogenetic significance, and preexisting genera have been hetero- 

 geneous as well as very poorly known. With the establishment of 

 some comparatively severe generic deffiiitions (only comparable 

 however to those used in other phases of systematic zoology), it 

 seems possible to summarize general impressions and ideas accumu- 

 lated during this study of Cambarincola. 



Althouo-h the BranchiobdeUidae is a normally homogeneous family 

 as regards general organization of body form and organ systems 

 histology, and way of life, a very considerable variation affects the 

 structme of the reproductive systems. A basic dichotomy was made 

 by Goodnight (1940) in recognizing two subfamilies according to the 

 distribution of male germinal tissue. For species m ^hich testes- o^^ 

 the morulae which they produce, occur only m segment vi. Goodnight 

 proposed a subfamily Branchiobdellinae ; for those m -l^f ^P^™^^" 

 [ozoa are produced in segment v as weU as vi>/^e Provided the name 

 Cambarincolinae. This difference, of course, had already been used 

 by Pierantoni (1912) as a generic character, and does appear to be a 

 fundamental distinction, particularly as it is reinforced at least m the 

 one species of Branchiohdella which I have exammed by correspond- 

 ingly important differences in organization of the larger and more 

 ectal parts of the male reproductive system. 



Another basicaUy important, anatomical distinction between genej^a 

 emphasised by several workers is the nature ot the »" "^t °f ^he 

 antenor nephridia. In some genera the two dncts open t" th« »" " 

 side independently ot each other; in others there is a commonly shared 

 nephridiopore. However, the nature of this relatrondnp is often (m 

 Let sually) difficult to detect with complete confidence and we a,^ 

 denied the use ot literature reports based on «- study of «*ole mount. 

 In eases where the nephridiopore has been carefully studied ^J^^^J'^^ 

 of serial sections, it does afford strong presumptive evidence of 

 relationships. 



