510 Illinois State Laboratory of Natural History. 



a 2) — that bearing the third pair of eyes — is distinctly longer 

 than IV a 3, and in some examples the furrow al/al is 

 more or less distinctly discernible. 2. The annuli VII a 3 

 and VIII a 1 are relatively very much longer, and on the 

 dorsal side the secondary annuli and furrows are distinctly 

 developed. 3. XXVI a 1 is always marginally and some- 

 times completely separated on the dorsal side from a 2. 

 4. The relative lengths of the annuli of complete somites 

 differ in the two species. In M. sestertia the neural annulus 

 (a 2) is figured as of equal or greater size than the secondary 

 annuli, while in M. decora it is typically shorter than any of 

 these in the same somite. 



Reproductive Organs.— Testes (PI. XLIV., Fig. 23, t)— ten 

 pairs, situated at XIII/XIY to XXII/XXIII inclusive. The 

 vasa deferentia (vd) are glandular, and follow sinuous courses. 

 In somite XI they become narrow and lose their glandular 

 coating. Opposite to ganglion XI they turn abruptly into 

 the compact, massive, much convoluted epididymes (ep). 

 From the posterior end of each of the latter a wide somewhat 

 folded and coiled ductus ejaculatorius (de) leads to the term- 

 inal organ. Just before plunging into the outer glandular 

 and muscular wall of the latter the ducti become constricted, 

 and then form a pair of slightly enlarged sacs which proceed 

 upward side by side to open together into the end of the male 

 invagination (PI. XLIV., Fig. 22). This terminal male organ 

 (PI. XLIV., Fig. 23), which is evidently intermediate in its 

 structure and character between the atrium of H<emopis and 

 the genital pit of Philobdella, is, when entire, spherical in 

 shape ; but when its external coat of muscle fibres and pros- 

 tate glands (pg) is stripped off, the lining sac is found to be 

 somewhat pyriform (ati). 



The ovaries (PI. XLIV., Fig. 23, ov) are large and globular, 

 situated just behind ganglion XII, and ventral to the nerve 

 cord. Short paired oviducts (od) unite in a common oviduct 

 (ode) without any evident gland at the point of junction. 

 The vagina (va) is short, of irregular diameter, and bent on 

 itself. 



The copulatory glands (PI. XLIV., Fig. 23, egl), the external 



