334 Mr. E. Ray Lankester on the 



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

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

 Gephyrean/S'«};MncitZMS,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 AjmoW^ plus its perivisceral fluid. It is hence 

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

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

 of the vascular fluid. If such a nomenclature 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 hjemo- 

 chyle ; the circulatory fluid of Mollusca and Arthropods would 

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

 element in separate vessels, and in exceptional cases {Solen, 

 Planorbis, Ckironomus, Chirocephalus, DapJinid) hemoglobin 

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

 plem-o-peritoneal cavity, lymphatic canals, and vessels in Ver- 

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

 throughout the triplohlastic series, from the proliferation of the 

 connective-tissue corpuscles lining the walls of the lymph-spaces, 

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

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

 hffimochyle, 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 point 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 polychaatous 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 



