T. B. ROSSETER ON DREPANIDOT.ENIA YEXU8TA. 11 



follow the borax-carmine process so strongly recommended by 

 some German investigators, but I hardened with chromic acid, 

 and stained with Ehrlich's acid hoematoxylin. I find this a better 

 differentiating medium than borax-carmine. 



Methods. — I first immersed the tapeworm en masse in glycerine 

 diluted with alcohol for forty-eight hours, then washed for a few 

 minutes in a Aveak alcoholic bath, cut the strobila into pieces and 

 left the severed parts in a '25 per cent, chromic acid solution for 

 three days, passed them on to methylated spirit for three days 

 ^changing the spirit each day), stained with hsematoxylin, 

 watching them carefully so as not to over-stain ; washed in tap- 

 water, embedded in parafiin, cut into sections with microtome, 

 passed through absolute alcohol, cleared with clove oil, and 

 mounted in Canada balsam. 



I shall now describe the Scolex, the Strobila, the Generative 

 Organs, both male and female, and the Eggs or Oncospheres. 



The Scolex. — The scolex in a fresh specimen has the appearance 

 of a beautifully symmetrical cup or bowl (Fig. 1), with four globular 

 suckers (Fig. 1, a) placed equidistantly round it; the upper peri- 

 phery of each sucker coalescing with the rim of the scolex ; and 

 they stand out somewhat prominently in the form of a boss, or 

 protuberance, and so symmetrically are they placed, that when an 

 unprepared scolex is flattened between two plaques of glass it 

 forms a perfect square; and the compressed half -circle of each 

 sucker lies within a triangle whose apex is in the centre of 

 the scolex. Their diameter in flat specimens is 0*280 mm. The 

 rostellum (Fig. 1, h) springs from the centre of the bowl. It is 

 a, retractile organ, and when everted it is seen to be claviform. 

 Its anterior end is a flat surface from which rises a dome or 

 crown ; the dome carries the eight hooks of the scolex, and is 

 much smaller in diameter than the platform on which its base 

 rests. The platform in its natural condition is circular ; but in 

 flattened specimens it has the appearance of being angular. The 

 hooks are sickle -shaped, and measure 0'051 to 0-054 mm. The 

 posterior end of the rostellum is attached to and penetrates the 

 cellular parenchymatous tissue of which the scolex is composed, 

 and when everted with the rostellum this cellular tissue forms 

 a dome above the rim of the bowl; but when the retractor 

 muscles invert the rostellum, it forces down this tissue of the 

 scolex, and we then get that bowl, or crater-formation, which 



