1892.] NEW SPECIES OF EARTHWORMS. 145 



records are scanty. In Criodrilus I mention \ briefly, the " hemi- 

 spherical gland, which may be called a prostate," and which " con- 

 sists of ceils similar to those forming the epidermis of the clitellum 

 and quite continuous with them ; the gland appears to be formed 

 only by a hemispherical thickening of the epidermis over this area." 

 Rosa " refers to this organ as " atrium." In the case of Callidnlus, 

 Michaelsen^ states that this "doubtful prostate" consists of small 

 granular cells, with indistinct boundaries, the nuclei sometimes being 

 scarcely recognizable ; in the same place he describes — -though very 

 briefly — structures of the same nature as those in Micr. i^apillata 

 as occurring in Kynotus madagascariensis ; to which I shall refer 

 later on in this paper. 



The nature of the organ in Qeoscolex is unknown. But Micro- 

 chceta (and probably Kynotus) differs from the rest in that this 

 gland is entirely independeut of the sperm-duct ; whereas in pros- 

 tatiferous worms (that is, those of the families CryptodrilidcB, 

 Perichcetidce, Acanthodrilidce, Eudrilidce, &c.) this gland is always 

 in connection with the sperm-duct, or in its immediate neighbourhood ; 

 moreover, it is tubular in general character and is apparently a more 

 efficient organ of copulation than in these other cases. 



We are in ignorance of the real function of the prostate or of the 

 " genital duct " in these prostatiferous worms ; but there is, pro- 

 bably, a protrusion of the muscular duct during co{)ulation, and an 

 insertion thereof into the spermatheca, as there is undoubtedly 

 in such forms as the Tubificidee : but in the case of Microchceta 

 such a penial function is impossible, for there is no sac into 

 which such a papilla could be inserted ; it probably, however, 

 serves as a sucker. The small papilla in the terminal pit of the 

 larger one, the muscular arrangements, and the folded cavity suggest 

 such a sucking-organ ; and, no doubt, the copulating chsetse serve to 

 aid this apparatus in holding on to another worm ^. 



It is not necessary to think that this sucking-apparatus in Micro- 

 chceta is the forerunner of the prostates with their protrusible duct, 

 though it is quite possible that this latter organ may have arisen 

 from some such apparatus as is present in Brachydrilus, Geoscolex, 

 &c., where the " sucker " is perforated by the sperm-duct. During 

 copulation in Lumbricus, &c., the ventral surface of the clitellum 

 itself, bounded b}' the tubercula pubertatis, very probably acts as 

 a sucker ; here in Microchceta a more specialized apparatus, on 



I " Studies in Earthworms, III.," Q. J. M. Sc. xsvii. p. 568. 



■^ "Sul Criodrilus lacuum," Mem. d. E. Accad. d. Sci. d. Torino, ser. 2, 

 torn, xxxviii, 



3 " Terricolen d. Berliner Zool. SammL," Arch. f. Naturgeach. 1891. 



^ Eosa describes (Ann. d. k. k. Natur. Hofmus. 1891) certain glandular 

 bodies in M. benhami (in somites si. to xxviii.) which appear to have a some- 

 what aimilai- structure ; but he mentions no external papillae : he compares 

 them with the " pyriform glands " of Urobenus and Urochceta, and suggests, as 

 I have done, their possible connection with the prostates of other worms ; and 

 his species forms an interesting link between the arrangement in Urobenus and 

 M. papillata, though the structures ia M. henhami do not appear to have any 

 copulatory functions. 



Proc. Zool. Soc— 1892, No. X. 10 



