1865.] Mr. Bastian Anatomy and Physiology of Nematoids. 373 



the oxidating portion of the process of respiration, and thinks that this 

 deficiency may be compensated by a greatly increased activity of glandular 

 eliminating organs. Considering the conditions under whose influence so 

 many of the parasitic forms pass their existence, we can easily imagine that 

 the presence of any organs for effecting an oxidation of their tissues would 

 not only be useless, but actually baneful. Glandular organs exist in the 

 greatest abundance in all Nematoids, and many of these are excretory organs. 

 In those species in which no modification of the ventral excretory apparatus 

 is met with, the author has found a very large number of channels 

 running through the chitinous portion of the integument, so as to bring 

 its deep cellular layer in communication with the exterior. These pores 

 are, he believes, complementary respiratory organs, and their development 

 is always in an inverse proportion to that of the other excretory organs. 

 Thus amongst the free Nematoids he has found them most numerous in 

 Dorylaimus stagnalis and Leptosomatum figuratum species in which the 

 ventral excretory apparatus is entirely absent. The same arrangement is 

 met with in the Trichocephali and Trichosomata, in which these integumental 

 channels attain their maximum development. The gradually widening 

 longitudinal band long known to exist in the Trichocephali is due to the 

 presence of thousands of these channels in connexion with a glandular de- 

 velopment of the deep integumental layer beneath. 



Many interesting facts are brought forward concerning the " tenacity of 

 life " of some of the free Nematoids, and their power of recovery after pro- 

 longed periods of desiccation. This has been long known as one of the 

 characteristics of Tylenchus tritici*, but the author has found it common 

 only to the species of four land and freshwater genera, Tylenchus, Plectus, 

 Aphelenchus, and Cephahbus. The remainder of the free Nematoids are 

 remarkably frail, and incapable of recovering even after the shortest periods 

 of desiccation. 



In the last section, on "The zoological position and affinities of the 

 Nematoids," the author enters fully into what he believes to be the points of 

 resemblance between these animals and the Echinoderms. The strongest 

 evidence is, he thinks, to be found in the fact of the very close resemblance 

 between the nervous systems of these animals, differing notably as it does 

 at the same time from what we find in the Scolecida or Annelida. Then 

 the integumental pores which he has now discovered in so many Nematoids 

 can, he thinks, be paralleled only by the ambulacral and other pores met 

 with in the Echinoderms. Great similarities in the distribution of these 

 pores may also be observed in the two groups. The Nematoids present 

 no trace of segmentation or lateral appendages to their bodies, but traces 

 of a radiate structure do exist. Their various parts and organs exhibit a 

 quadrate mixed with a ternate type of development. He looks upon the 

 order Nematoidea as as aberrant division of the class Echinodermata, 

 which at the same time tends to connect this class in the most interesting 

 * Vibrio tritici of older writers. 



VOL. XIV. 2 F 



