300 NATUKAL HISTOEY SOCIETY OF DUBLIX. 



soon regularly segmented. Its first stages of segmentation escaped my 

 observation; and many ova presented six, nine, or more globules of the 

 parted yolk when first I examined them (Tigs. 9, 10, 11). Soon the 

 mass became finely granular, and assumed an elliptical shape, which in 

 some became curved or arcuated. The two extremities then begin to be 

 differentiated, and from the posterior end a lateral turn or projection 

 extends, at first short, but soon considerably elongating, until it becomes 

 remarkably like the tail of the adult, twisted to one side (Fig. 12). The 

 anterior end becomes blunt, and somewhat flattened, and no granules 

 appear in it. At this stage in some of the more perfect a moniliform 

 thread appears to pass down the centre of the body from the mouth 

 to the root of the tail projection, forming the primitive trace of the 

 alimentary canal (Figs. 13 and 14). I was not able to observe the deve- 

 lopment of the reproductory apparatus ; but it is probable that it does 

 not appear until the young animal has become liberated from its shell. 

 All the changes which I have noted took place inside tbe oviduct of the 

 mother ; but I also observed ova floating in the surrounding fluid in 

 similar conditions of development. 



The male sexual organs are made up of — first, a testis — tubular, and 

 elongated, but not so long as the ovary ; this begins small, and rapidly 

 thickens, until it rivals the intestine in size (Fig. 1, d). This is at first 

 filled with an indistinct granular material, but afterwards contains more 

 perfectly elaborated spermatic fluid. These tubes are not easily unra- 

 velled ; and in some males (probably those which are immature) the 

 whole glandular mass appears as though it were a lobulated indivisible 

 structure. Near the posterior extremity of the body the testicular tube 

 ends in a large, dark, rough, bilobed seminal vesicle (Fig. 1 , e), which 

 lies on the ventral surface of the intestine, and sends off below a narrow 

 duct (Fig. 1, g) to the root of the intromittent organ. In front of the 

 blunt bevelled tail projects the spicula — a slightly curved body, with a 

 pointed pen- shaped extremity ; half of it is included in a canal in the 

 animal's body, from which it passes by a small opening, whose smooth 

 projecting margins overlap its sides for a short distance (Fig. 1, h). 



A little in front, and to the side of the large spicula, a smaller one 

 is seen, much more acute, and communicating with the spermatic vesicle 

 by a small canal. This second smaller organ did not escape the atten- 

 tion of Dujardin ; and it was noticed by that naturalist as a character 

 marked enough to separate this species from Ascaris, and to elevate it 

 into a genus by itself. To this distinction I think we will be able to 

 confirm its claim after our careful examination — first, on account of 

 its unequal spicula ; secondly, from its rudimentary caecal secreting ap- 

 pendages ; thirdly, from the comparative indistinctness of its oral tu- 

 bercles ; and so, following the great French helminthologist, I think we 

 are justified in naming it Atradis dactyluris. 



I cannot close these remarks without taking the opportunity of 

 recognising my obligations to Dr. John Barker for his invaluable assis- 

 tance in the course of my investigations, in verifying from indepen- 



