384 ADAM SEDGWICK. 



liar cellular tissue which has been described by Gaffron (No. 3) 

 in the pericardial cavity of the adult. Gaffron compares this 

 tissue to the fat bodies of other Tracheates, a comparison with 

 which I am inclined to agree, although I am not aware that 

 fat bodies are as a rule present in the pericardium. 



Mr. Heathcote, however, informs me that in the Myriapoda 

 a portion of the fat body does lie in the pericardium, and 

 resembles in its relation to the heart the pericardial tissue of 

 Peripatus. A tissue exactly like the pericardial tissue is found 

 in the lateral compartment of the body cavity (PI. XXVIT, 

 fig. 11). It has been noticed by Balfour and Gaffron. It 

 seems to me probable that this tissue, which lies in the vascular 

 system, is of the same nature as the lymphatic tissue of the 

 Vertebrata, with which it undoubtedly presents many points of 

 resemblance. The botryoidal tissue of Leeches (Lankester) and 

 the brown cells of Clnetopoda may possibly fall into the same 

 category. The former presents very much the same relations 

 to the vascular system, but the latter differs by lying in the 

 coelom. 



In Stage g the horizontal septum which divided the cerebral 

 compartment of the body cavity into a dorsal (b. b. c.') and 

 ventral (b. b. c, Part III, fig. 43) chamber breaks down. 



Both the pericardial and lateral compartments of the body 

 cavity (hsemoccele) seem to communicate with spaces amongst 

 the muscles of the body wall. One such set of spaces is especially 

 conspicuous between the ectoderm of the ventral body wall and 

 the circular muscles (PI. XXVII, figs. 11, 17). This system of 

 spaces, which is probably segmentally arranged, communicates 

 with the spaces in the legs. It is, I think, the blood in these 

 ventral vascular channels which exudes through the ventral 

 organs when the animals are contracted by the action of 

 chloroform. 



The ostia of the heart appear to arise in Stage g. I have 

 no satisfactory observations of them. They are, I think, con- 

 fined to the posterior end of the heart in the Cape species. 



The main vascular tracts, therefore, are five in number, or, 

 to put it in another way, the h^emocqsle is divided into five 



