THE REGION OF THE SPINAL CORD 421 
bodies is a property of the leucocytes, and that these leucocytes which 
are found in the ccelomic spaces of the Annelida, etc., are apparently 
derived from the epithelium of such spaces. Also by the prolifera- 
tion of such epithelium in places, ¢.g. the septal glands of the terres- 
trial Oligocheta, segmental glandular masses of such tissue are 
formed which take up the colouring matter, or the bacilli. In the 
limicolous Oligocheta 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, zc. must be derived from cclomic epithelium, 
even when all evidence of any ccelom 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 
