ON AMPHILINA PARAGONOPORA 71 



and of much denser consistency, and (2) oval egg-shells but 

 little inferior in size to the larvae and containing only a few 

 large dissociated blastomeres of different sizes (PL 4, figs. 87, 

 39). These practically empty egg-shells were extremely 

 numerous — from five to ten times more numerous than the 

 oval larvae. They are best displayed by macerating portions 

 of the Amphilina» either fresh or preserved, in Marcacci's fluid 

 (equal parts of nitric acid, glycerine, and water) over-night, 

 followed by teasing or, better still, by grinding up on metal 

 gauze suspended in water with a piece of flat wood — the 

 products of the grinding sink through the gauze and can he 

 collected by centrifuging. Lest it be thought that the half- 

 empty condition of the egg-shells was due to the Marcacci's 

 fluid, I may mention that I obtained the same result with 

 simple maceration in water (PI. 4, fig. 39) and that Marcacci's 

 fluid does not damage even such objects as spermatozoa ; the 

 half-empty egg-shells can also be seen, as already mentioned, 

 in whole-mounted specimens and in serial sections mounted in 

 balsam. I may also mention that it was only by employing 

 Marcacci's fluid that I first detected the filament or tag on the 

 egg-shells, it usually being difficult to see this structure in 

 sections and whole mounts. I suspect that similar maceration 

 would display a tag on the egg-shells of A m p h i 1 i n a magna, 

 Southwell. 



The half-empty egg-shells undoubtedly represent larvae that 

 have degenerated. It is conceivable that if for any reason 

 a worm cannot escape from its fish host, the larvae degenerate 

 in consequence of not being liberated into water. Facts cited 

 in Part II afford additional evidence in favour of this view. 



{h) K e - d e f i n i t i o n of the Genus A m p h i 1 i n a, a n d t h e 

 chief Distinctions between the five Species. 



Wagener's definition of the genus Amphilina (9) must be 

 amended in order to comprise the facts that in A. para- 

 gonopora the body is ribbon-shaped, the posterior end is 



larvae (which are the same length as the largest larvae I have seen in 

 utero) are abnormally small. 



