DESCRIPTIONS OF GENERA AND SPECIES 211 



genera, which is, however, not borne out in other particulars. It is true that 

 among earth-worms it does not seem possible to lay much stress upon the existence 

 of one or of two pairs of sperm-ducts ; but the existence of two pairs is so rare an 

 occurrence among these aquatic forms that it seems to have more importance; hence 

 it appears to me to be quite justifiable to found a family character upon it. 



Although it is difficult to institute any affinities between the Lumbriculidae and 

 the higher Oligochaeta, their relationships to the lower forms are, perhaps, rather 

 more obvious; as Vejdovskt (24) has said^ the genus Stylodrilus is in certain 

 particulars not far removed from the Tubificidae; this genus has not the branched 

 caecal appendages of the dorsal blood-vessel. A better intermediate genus or, rather, 

 family, for I have placed it in a distinct family here, is Eclipidrilus ; that genus 

 has the caecal appendages of the Lumbriculidae, but it has also spermatophores 

 which are quite unknown in the Lumbriculidae ; I have also called attention to 

 the structure of the spermiducal gland, so far as we know it, as affording evidence 

 of a resemblance to the Tubificidae ; the position, also, of the oviducts in the genus 

 Eclipidrilus is more like what is found in the Tubificidae than the position which 

 characterizes the Lumbriculidae. 



The Lumbriculidae, however, also show affinities to the Naidomorpha ; this is 

 chiefly seen in the nephridia; in both these families (and also in Ilyodrilus — a low 

 form of the Tubificidae) there is a conspicuous brown mass immediately following 

 the funnel of the nephridium; nothing of the same kind occurs in any other group 

 of Oligochaeta. 



Ltjmbricultjs, Gkube. 



Lumbrioulus, Geube. non Clapaeedb. 

 Lumbrieus, 0. F. Mullek (in part.). 

 Saenuris, Johnston. 

 ? Acestus, Leidy. 

 DEPiiTiTioii. Greatly elongated worms, aquatic in habit. Setae bifid at extremity. 

 In each segment, after eighth, a pair of blind branched diverticula of dorsal 

 vessel, and a pair of non-contractile perivisceral trunks uniting dorsal and 

 ventral vessels. Spermiducal glands in VIII. Spermathecae in X, XI, XII. 

 Oviducts in X, XI. Albumen-glands in IX. 

 DiEFFENBACH has lately given strong reasons for believing that Gkube and CLAPARiiKE did 

 not base their descriptions of Lumbriculus variegatus upon the same species, or even upon the same 

 genus. Clapaebde himself remarked (2) upon the differences between the facts observed by 

 himself, with reference to the structure of this worm, and the description given by Grube, but, 



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