MACALISTER — ON ASCARIS DACTTLUR1S. 295 



scribed by the latter naturalist in his " Synopsis Entozoorum," as " As- 

 caris dactyluris capite nudo, corpore utrinque sequaliter attenuato; 

 cauda fceminaB longa subulata, maris apice brevis obtuso depresso an- 

 tequam spicula passim substantia passim egressa vasa in vaginam 

 fimbriatam."* In his subsequent description he refers to it as being 

 found in great abundance; he obtained " multa millia specimina ut 

 maximas ftecum pars iisdem constaret," exactly according with my own 

 experience, as stated above. He likewise describes it as being from 

 two to two and a half lines long, with a three-valved head ; a straight 

 narrow oesophagus, which is longer in the male than in the female , a 

 subglobose stomach, and elliptic oblong ova, each with a large and 

 obversely divided nucleus. There are several points of greater or less 

 importance which he has omitted in his description ; but, on the whole, 

 these characters are very distinct. Dujardin, in the Appendix to his 

 work on "Intestinal "Worms," refers to this animal, and states his opinion 

 that it should be separated from the genus Ascaris, on account of its ob- 

 scurely bi- or trilobate mouth, and its unequal spicula. He does not 

 enter into any further details respecting its structure, but expresses his 

 regret at not having been able to fulfil his original intention of tho- 

 roughly examining its internal organization. A few notices of this species 

 likewise occur in Siebold's "Anatomy of the Invertebrates;" but, with 

 these exceptions, I am not aware of there being any special anatomical 

 description of this creature extant. 



The specimens which I have been enabled to examine are whitish 

 in colour, mostly straight, though at times a little curved at the distal 

 extremity, and measuring, as an average, about two lines and three- 

 fifths in length — the range being from one line and a quarter, as a mi- 

 nimum, to five lines as a maximum ; the breadth in the centre varies 

 from one-tenth to one quarter of a line, and in some of the largest ex- 

 ceeded that amount. The males (Plate III., Pig. 1), which are very 

 much fewer than the females (at least among those that I examined not 

 one in fifty was a male), are much smaller, and average in length a line 

 and seven-eighths ; they are more curved than the latter, and sometimes 

 exhibit a partial dorsal constriction at the junction of the anterior and 

 middle thirds. The females (Plate III., Pig. 2) are usually about two 

 and a half to three lines in length. 



The integument is transparent, chitinous, wrinkled transversely, or 

 annulated; but this appearance is not always distinct in recent specimens, 

 or in those kept in aqueous solutions. When, however, they are immersed 

 in any dense fluid, which will cause a rapid exosmosis, the animal be- 

 comes slightly shrivelled, and the annulations are then seen with the 

 utmost clearness. When placed in spirits of wine, the integument be- 

 comes firmer, and less transparent, and the annulations also seen with 

 considerable distinctness ; a few longitudinal strios are visible on the 



* Loe. cit., pp 40, 272. 



