PARASITIC WORMS LEIPER AND ATKINSON'. 



I 'J 



The genital atrium is very large and lias a fleshy wall. The pores are single and 

 on the same side throughout the strobila. The massive atrium occupies nearly the 

 whole border of the segment. The outer measurement of the atrium is 0*23 mm., while 

 its cavity is 015 mm. across. The cirrus (sp) is usually extruded and hooked hack- 

 wards in nearly every segment. It measures 0'05 mm., and its surface is roughened 

 by ridges. The broad vagina crosses the segment, and, after turning once upon itself, 

 runs towards the centre. Two excretory canals run down either side, immediately 

 internally to the genital atrium, throughout the segments. The outer canal is small, 

 the inner nearly twice as wide. 



30. Tetrabothrius priestleyi, Leip. and Atk. (PL IV, fig. 28.) 



Tetrabotlirius priestleyi, Leiper and Atkinson, Proc. Zool. Sue, 1914, p. 225. 



Strobila 10 cm. long, excessively slender, with large tulip-like head. Testes 17-20. Near to 

 T. pelecani, Fuhrmann. 



Host. — A Frigate bird (Fregata aquila or F. ariel), shot at South Trinidad 

 (Stat. 36) ; intestine. 



External Appearance. — The worms measure from 10 to I I cm. in length, and for 

 the greater part are exceedingly slender. The segments become enlarged only towards 

 the caudal end. They are pearly white in the anterior thin part, changing to yellowish- 

 white posteriorly. The worms were removed from the intestine in a tangled mass, and 

 owing to their long slender necks were difficult to separate from one another. 



Head. — The head is comparatively large, and is armed with four suckers placed on 

 t he sides and not showing on the top of the head. The suckers are narrow in front 

 and expand to their greatest width behind. The head is 0'55 mm. long, and attains 

 0'44 mm. in breadth at its broadest part. Each sucker is 0*42 mm. long and 0"22 nun. 

 wide at its broadest part. The head-region is well-defined. There is a slight con- 

 striction behind the suckers, and this is succeeded by a fairly long neck, before the 

 segments make their appearance. 



Segment*. — The segments figured (IM. IV, fig. 28) are from about the middle of 

 the worm. .Maturity is late. The segments stain diffusely with haematoxylin. They 

 are broader than long, measuring 0'(i mm. by 0*3 mm. Their shape does not vary 

 much, but they become thicker and broader toward the posterior end. The genital 

 atria, are unilateral, large and rounded, measuring 014 mm, They open laterally. 

 The cirrus is rounded and unarmed, measuring O'l mm. in length and 0"06 mm. in 

 its greatest breadth. A short vagina lies behind it. The testes are relatively large 

 and form about seventeen to twenty groups. They are confined to the central part 

 of the segment. In some of them the bulk is increased markedly, and stained 

 nuclei are found only round the periphery. The volk-gland is placed in front of 

 them, in the middle of the cephalic border. It is large, circular, and stains deeply, 

 measuring 0'04 mm. across. A single excretory canal runs down either side, externally 

 to the testes. The canal is broad and runs internally to the genital atrium. A most 



