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XXI. On the Anatomy and Physiology of the Nematoids, Parasitic and Free; with 

 observations on their Zoological Position and Affinities to the Echinoderms. By 

 H. Chaklton Bastian, M.A., M.B. Lond., F.L.S. 



Received June 13, — Read June 15, 1865. 



CONTENTS. 



Page 



Introductory Remarks 545 



Tegumentary Organs and Appendages 547 



Muscular System 559 



Nervous System 565 



Organs of Sense 572 



Organs of Digestion 573 



Glandular System 581 



Organs of Circulation — ' Water- vascular System,' &c 584 



The function of Respiration — how performed ? 602 



Organs of Generation 604 



Development and life-history 606 



Povrers of repair and tenacity of life 611 



Zoological Position and Affinities 620 



Although the parasitic Nematoids have been so long known and frequently submitted 

 to anatomical examination, it is somewhat surprising that, even up to within quite a 

 recent period, nothing was certainly known with regard to the arrangement in them 

 of the nervous system, or as to whether they possessed any modification of the organs 

 of circulation. The existence of both these systems has been asserted and denied over 

 and over again by successive observers, and conflicting statements in this particular 

 field of research have been so rife, that a well-known writer*, recently alluding to 

 this subject, even goes so far as to state that the many discrepancies in the accounts 

 given by leading Helminthologists of Nematoid anatomy "tend to throw great doubt 

 upon the general value of histological observations among the Helminths." Although 

 far from sharing in this opinion, I must admit that the tangled network of opposing 

 statements is sufiiciently disheartening. 



As a necessary consequence of our deficient knowledge of the real anatomy of these 

 animals, this order Nematoidea has been a continual stumbling-block in the path of 

 the philosophic zoologist. What is their place in the animal kingdom 1 A question, 

 surely, impossible to answer whilst so many doubts hung over the question of the 

 arrangement of their nervous and circulatory organs ; and it seems to me that many of 

 the erroneous opinions which have been held concerning these parts may be traced to 



• Dr. CoBBOLD, ' Entozoa : an Introduction to the Study of Helminthology,' 1864, p. 363. 

 MDCCCLXVI. 4 



