175 



Eisen distributed the eight genera he examined in this connection 

 as follows : having the mesenchytraeid type of bulb — Mcsenchytrcuiis; 

 having the enchytrreid type of bulb — Bnchytrccus and Michaelsena; 

 and having the lumbricillid type of bulb — Lumbricilhis, Marionina, 

 Bryodrihis, Hcnlca, and Fridcricia. 



Eisen was convinced that the structure of the penial bulb is of 

 ''great taxonomic importance" and he used it as the chief character 

 in distinguishing subfamilies, added it to the definitions of the genera, 

 and gave it a prominent place in his descriptions of new species. 



The family Bnchytrccidcc now contains sixteen genera and nearly 

 three hundred species. Since Eisen's investigation was based on about 

 fifty species distributed among eight genera it is evident that his work 

 must be extended and his conclusions tested on other species and gen- 

 era before the structure of the penial bujb can be considered as a safe 

 diagnostic character. Considerable work has been done on foreign 

 Bnchytrcridcc since 1905, but it has been in the formi of numerous 

 small papers, no comprehensive works having appeared. As a conse- 

 quence the systematic value of the penial bulb has been but little dis- 

 cussed. Stephenson ('11, p. 54) is inclined to discredit the use of the 

 penial bulb "as a basis for the distinction of subfamilies or, even, per- 

 haps, of genera." Most other foreign workers have been noncom- 

 mittal on the subject. 



There is no doubt that the discovery of taxonomic characters in 

 the structure of a rather conspicuous internal organ such as the penial 

 bulb is a step in adv'ance, and the desirability of adding to the some- 

 what limited list of specific and generic characters in Bnchytrcridce is 

 obvious to any one who has worked in the group. The writer has 

 given special attention to the structure of this organ in all of his work, 

 and critical studies have been made on all of the species and genera 

 available, not only with the view of determining the minute structure 

 of this interesting organ, but also to test the validity of Eisen's con- 

 clusions as to its systematic significance, hoping to add something 

 new, if possible, to the data already accumulated. 



Some interesting results have been obtained. In some cases they 

 lend support to Eisen's conclusions ; in others it is apparent that cer- 

 tain limitations and alterations must be made in Eisen's system; and 

 in still others it is clear that certain generic differences given by Eisen 

 do not hold. Owing to the importance of this subject the results of 

 the present study will be discussed in some detail. The studies of the 

 waiter on the penial bulb have been made on fourteen species dis- 

 tributed among five genera, namely, Henlea (urbanensis and iiiod- 

 erata n. spp.), Marionina {forhescc Smith and Welch), Lumbricillus 

 (rutilus n. sp. and insidaris Ude), Bnchytrcens (gillettensis n. sp. and 



