366 W. BLAXLAND BENHAM. 



the various constituents. I have already referred to the un- 

 certainty as to the precise somites to -which the different organs 

 belong, which has resulted from the descriptions of Perrier, 

 Beddard, and Horst. But now that a greater number of 

 species are known, some of them of fairly large size, we find 

 Perrier's original statements are correct with regard to the 

 position of most of the genital organs, and that Horst's num- 

 bers alone differ by being greater by a single unit. Beddard's 

 original description has been modified by his discovery that 

 his apparent first somite really consists of Somites i and ii. 

 The positions attributed to the organs in the species examined 

 by Eosa and Michaelsen, and in the present one, all agree 

 with Beddard's amended and Perrier's original numbers. But 

 nevertheless there still remain certain points on which some 

 discrepancy or uncertainty exists, both with regard to exact 

 position and minute structure. Some of these I hope to clear 

 up, or at any rate to advance, though, owing to the poor con- 

 dition of the worm, my contribution to the histology of 

 Moniligaster — of which we know very little indeed — is very 

 imperfect. 



The single pair of sperm-sacs (figs. 3 — 5) occupies partly 

 Somite ix and partly x. On the animal's left side the sac 

 appeared to be strung up by the Septum ix/x attached round its 

 equator. In reality the septum is pouched, and the sperm- 

 sac, as figs. 3 and 4 will show, projects into Somite ix through 

 the wide aperture of this pouch. 



On the right side, however, the pouch was deeper, so that 

 at first sight the sac appeared to lie entirely in Somite x ; but I 

 could trace the Septum ix/x behind the sac, and sections show 

 me that the sperm-sac belongs, as Beddard has already sug- 

 gested, to Somite ix. 



Each sperm-sac is nearly spherical, and is not so simple as 

 in M. Barwelli, for I find that the cavity is not un- 

 divided, as Beddard figures and states, but is traversed by 

 bundles of muscular fibres in different directions (fig. 5, trab.), 

 between which lie the groups of developing spermatozoa. The 

 trabecular structure is certainly not so highly developed as 



