ENTOZOA. 55 



lahis. Now he was a German ; but it was ascertained that he paid 

 occasional visits to a friend in Switzerland. There, doubtless, the 

 germ of the parasitic worm was introduced into his body. The count- 

 less ova of the taeniae, with their hard crusts or shells, and tenacity 

 of latent life, are, doubtless, widely dispersed, and need only the' 

 accidental introduction into an appropriate nidus for ulterior develop- 

 ment. 



LECTURE V. 



ENTOZOA. 



The essential anatomical character of the third order of Entozoa in 

 the classification of Rudolphi may be represented by combining the 

 head of an unarmed Taenia, with one of its joints, containing the fully 

 developed androgynous organs. The digestive system would then be 

 represented by a simple bifurcating canal, each fork ending in a cul 

 de sac. 



The Trematoda may be characterised as having a soft, rounded, or 

 flattened body, with an indistinct head, provided with a suctorious 

 foramen, and having generally one or more sucking cups for adhesion 

 in different parts of the body ; the organs of both sexes are in the 

 same individual. 



The great entozoologist Rudolphi, a pupil and ardent admirer of 

 Linnaeus, adopted external and easily recognisable characters for the 

 generic subdivisions of the Trematode order, the species of which were 

 distributed according to the number and positions of the suctorious 

 orifices and cavities. When there is a single one, it constitutes the 

 genus Monostoma : when there are two, which are terminal or at 

 opposite ends of the body, you have the character of the genus 

 Amphistoma : when the posterior of the two suckers is not terminal, 

 but on the inferior surface of the body, this constitutes the genus 

 Distoina : three suctorious cavities characterise the genus Tristoma; 

 five, the genus Pentastoma ; and a greater number that called Poli/- 

 stoma. Subsequent anatomical investigations have led to the forma- 

 tion of other genera of Trematoda, and have likewise shown that 

 those species which were grouped together by the external and arti- 

 ficial characters of the Rudolphian system, manifest differences of 

 organisation, indicating, at least, the generic distinction of such 

 species : nay, most of the Pentastomnta of Rudolphi appertain to the 

 Ccelelminthic class of Entozoa. 



E 4 



