334 Mr. E. Eay Lankester on the 



communication with the rest of the blood-ljmph-system. This 

 is very generally the case in Annelids ; not so, however, in the 

 GephyreanAS'«}j'u?icw?^/5, where the tentacular vessel communicates 

 periodically with the perivisceral space. In Vertebrates the 

 haemoglobin-bearing or respiratory system and the lymph- 

 bearing sinus-system communicate at various points, so that the 

 fluid in the former is complex, being comparable to the respi- 

 ratory fluid of an Annelid plus its perivisceral fluid. It is hence 

 hsemochyle or blood-lymph, if we limit the significance of 

 "blood" to that which it really connotes, namely the red part 

 of the vascular fluid. If such a nomenclatm'e be admissible, 

 viz. the limitation of "blood" to the respiratory element, then 

 the fluid in the closed vascular system of Annelids would be 

 blood, the perivisceral fluid lymph ; the perivisceral fluid of Gly- 

 cera with its red corpuscles would be blood-lymph or heemo- 

 cliyle ; the circulatory fluid of Mollusca and Arthropods would 

 also be haemochyle, since there is no separation of a respiratory 

 element in separate vessels, and in exceptional cases (Soleu, 

 Planorhisj Ghironomus^ Chirocephalus ^ Daphnia) haemoglobin 

 does appear in the common circulatory fluid ; the fluid of the 

 pleuro-peritoneal cavity, lymphatic canals, and vessels in Ver- 

 tebrates would be " lymph," and its corpuscles, derived^ as 

 ihroughoiLt the triplohlastic series j from the jyroliferation of the 

 connective-tissue cor2n(.scles lining the xoalls of the lymph-spaces j' 

 would be lymph-corpuscles or leucocytes; the fluid in the 

 arteries and veins, on the other hand, would be blood-lymph or 

 h£emochyle, being lymph added to other liquid and corpuscular 

 elements, the latter of which are respiratory and impregnated 

 with haemoglobin, whence they may be termed "pneumocytes." 

 As an illustration of the })oint which I wish to urge — viz. 

 that the various vascular and sinus systems of Triploblastica 

 are not to be regarded as important differentiations, but are 

 rather parts of one and the same primary blood-lymph-cavity 

 slightly modified or isolated — let me point to two facts. First, 

 among polychsetous Annelida we have generally a closed vas- 

 cular system and a perivisceral space ; in Glycera, however, 

 the shutting off of a part of the blood-lymph-space as a closed 

 system does not occur, but we have only the one great peri- 

 visceral chamber, with pneumocytes added to its corpuscular 

 contents, this change being unaccompanied by any other great 

 structural modification ; and it is a fact that "anangian 

 genera" occur in the same family with others possessing the 

 closed set of vessels, e. g. Aphroditacea. Secondly, in a 

 parasitic crustacean as yet undescribed, discovered by Prof. 

 Edouard van Beneden of Li^ge, there is developed a closed 

 vascular system lying within the regular blood-sinuses, and 



