THE REGION OF THE SPINAL CORD \2\ 



bodies is a property of the leucocytes, and that these leucocytes which 

 are found in the coelomic spaces of the Annelida, etc., are apparently 

 derived from the epithelium of such spaces. Also by the prolifera- 

 tion of such epithelium in places, e.g. the septal glands of the terres- 

 trial Oligochreta, segmental glandular masses of such tissue are 

 formed which take up the colouring matter, or the bacilli. In the 

 limicolous Oligochseta such septal glands are not found, but at the com- 

 mencement of the nephridial organ, immediately following upon the 

 funnel, a remarkable modification of the nephridial wall takes place to 

 form a large cellular cavernous mass, the so-called filter, which in 

 Euaxes is full of leucocytes ; the cells are only definable by their nuclei, 

 and look like and act in the same way as the free leucocytes outside 

 this nephridial appendage. As G. Schneider points out, the whole 

 arrangement is very like that described by Kowalewsky in the 

 leeches Clepsine and Nephelis, where, also immediately succeeding 

 the funnel of the nephridial organ, a large accessory organ is found, 

 which is part of the nephridium, and is called the nephridial capsule. 

 This is the organ par excellence which takes up the solid carmine- 

 grains and bacilli, and apparently, from Kowalewsky's description, 

 contains leucocytes in large numbers. We see, then, that in such 

 invertebrates, just as in the vertebrate, modifications of the true excre- 

 tory organ may give rise to phagocytic glands of the nature of lym- 

 phatic glands. Further, these researches of Kowalewsky suggest in 

 the very strongest manner that whenever by such means new, hitherto 

 unsuspected glands are discovered, such glands must belong to the 

 excretory system, i.e. must be derived from ccelomic epithelium, 

 even when all evidence of any cceloin has disappeared. Kowalewsky 

 himself was evidently so impressed with the same feeling that he 

 heads one of his papers " The Excretory Organs of the Pantopoda," 

 although the organs in question had been discovered by him by this 

 method, and appeared as ductless glands with no external opening. 



To my mind these observations of Kowalewsky are of exceeding- 

 interest, for it is immediately clear that if the segmental organs of 

 the annelids, which must have existed on all the segments of the 

 forefathers of the Crustacea and Arachnida (the Protostraca), have left 

 any sign of their existence in living crustaceans and arachnids, then 

 such indication would most likely take the form of lymphatic glands 

 in the places where the excretory organs ought to have been. 



Now, as already pointed out in Peripatus, such segmental organs 



