o-U^ l)v. Fiiiuz Liiw uti a new 



What i'unctioiis tliis organ porronus, and wliat ai"c its rela- 

 tions to the genital organs, is still nuknown. i)r, ,1. Kuhii 

 first discovereil this organ in the male of his Aii</uil/ula (lij>- 

 smu\ and he also found it impossible to Hnd any data for its 

 elueidation in his repeated observations of that worm. With 

 regard to the interpretation of this organ (which occurs in the 

 males of all the species of the genera Tt/lenc/u(s, Bast,, and 

 li/tabditi's, Duj.) 1 agree rather with Kuhu than with Bastian*, 

 being, like the former, of opinion that it is stretched like a 

 velum over the anal aperture; Avhilst Jiastian thinks that two 

 delicately membranous wings (''caudal ahe '') are attached to 

 the sides of the tail of the male, the contour of which is seen 

 under the microscope both in the lateral and dorsal position. 

 For if Bastiau's opinion were correct, the membrane must 

 appear much narrower in the lateral than in the dorsal posi- 

 tion of the animal ; but just the contrary is the case. 



The female genital aperture is also situated near the hinder 

 extremity of the body, and leads to a vagina directed vertically 

 to the longitudinal axis of the body, which opens outwards 

 with prominent margins, and there appears as a short trans- 

 verse cleft {vulva). The distance of the vulva from the hind- 

 most point is one eighth of the total length of the body. This 

 [caudal] jiart of the body in the female is always slightly bent 

 towards the ventral side, and does not diminish so rapidly as 

 in the male. As already mentioned, the granular and vesi- 

 cular contents of the body render all inspection of it almost 

 impossible ; and so I did not succeed in recognizing the in- 

 ternal sexual organs, the termination of the intestine, and the 

 anal aperture in the female ; on the other hand, 1 twice saw 

 distinctly, in the interior of the body of the female, (|uite close 

 to the vulva, a sharjily defined q^<^j which showed precisely 

 the same finely granular contents mixed with a few vesicles 

 as the numerous eggs lying loose among the worms. 



Males and females do not differ in length in this species. 

 The greater number of them are almost exactly 1 millim. in 

 length ; only a few do not reach this size, and remain only 

 0"9 millim. long. But as exce})tions exist almost everywheie^ 

 I found among the majority of females of nearly equal lengtii 

 one oil'3 millim. length, and of proportionately increased thick- 

 ness. As regards thickness, the males of the same length ap- 

 pear to be a little thinner than the females. It is, however, very 

 difficult to give perfectly accurate, reliable measurements for 

 creatures such as these little woims — as on the one hand, when 

 alive they are never still, but are constantly bending, stretching 



* •' Monoj-Taph on the Anguillulidfe," Traus. Linn. ?oc. vol. xxv. (]86(.)). 

 V. V2o. 



