PART III.] Development of Filaria in Tumours of Aorta of Dogs. 543 



i/fbe an immature worm, but manifesting considerable evidence of orgapisation and in 

 : a state of great activity. Tliey may be so small as not to exceed ^^'dx of an inch 

 in length or more than ylcyth transversely at the widest part. Some yield even 

 smaller measurements than this. 



At this stage of development no reproductive organs can be discerned. The 

 oral end terminates in two pointed papillae, dorsal and ventral, which can be brought 

 closely together, so as to form a sort of "borer," by which means, possibly, the 

 parasites bore their way through the tissues. (Plate XXXIX, Figs. 11 to 13.) The 

 alimentary canal is well differentiated, the oesophagus occupying above |^rd of the 

 entire length of the worm : a well-marked sphincter-like constriction exists a short 

 distance below the mouth, probably indicating the junction of the pharynx with the 

 oesophagus. The intestinal canal terminates on the convex surface, a short distance 

 from the end of the tail ; the latter is somewhat blunt, and is tipped with a 

 trefoil-like object (glandular ?), communicating with a tube and apparently containing 

 a transparent fluid. (Plate XXXIX, Fig. 13.) 



During this period of its growth the worm undergoes a moulting process — 

 casting off its skin entirely. (Plate XXXIX, Fig. 12.) When the cuticle has become 

 somewhat separated from the body of the worm shortly before the " moulting " 

 actually occurs, the continuation of the old cuticle with the lining of the oral and 

 anal orifices is very evident, as also the fact that it forms a coating to the tri-lobed 

 gland-like object at the caudal extremity. 



This process of moulting appears to be repeated several times, and each time 

 some slight modification occurs in the appearance of the worm, especially at both 

 ends ; it also increases in size. The prominent papillae with which the mouth is 

 furnished gradually disappear, and, by the time that the worm has acquired a length 

 of about l^ths of an inch, reproductive organs can be distinctly made out and the 

 sex identified. No ova, however, can be detected in the genital tube of the female 

 at this stage (Plate XXXIX, Fig. 14), and the spicula in the male are not developed 

 until after the spermatic tube and the sheath of the retractor muscles of the larger 

 spicule. The oesophagus is proportionally much shorter, and the tri-lobed object at 

 the caudal extremity almost completely disappears. 



The worm gradually acquires a more decidedly pinkish hue, and instead of 

 [occupying a little tumour alone, as it did when very small, it appears to make its 

 way into some adjoining tumour. Other worms also migrate to this, so that one 

 tumour may be common to several parasites. It should, however, be noted that they 

 do not all occupy a single cavity, but each tumour is tunnelled in various directions, 

 80 there is frequently some difficulty in pulling out the parasites without tearing or 

 otherwise injuring them. 



Sometimes they may be seen to have crept outside the tumour, lying between 

 it and the serous covering investing the artery, or a parasite may be seen emerging 

 through a minute orifice communicating between the tumour and the interior of the 



