XXVI. 

 THE BLOOD-CORPUSCLES OF THE ANNELIDES. 



Professor Lankester. in a recent number of the ' Quarterly 

 Journal of Microscopical Science 1 / (January 1878, p. 70-73), makes 

 certain statements relating to me, the chief tangible basis for which 



1 Professor Lankester writes as follows : — ' The entirely original introduction of 

 Branchiobdella into the list of Annulata with corpusculated ' pseud-haemal fluid ' is 

 difficult to explain, since, from what follows, it seems unlikely that Dr. George 

 Pvolleston had made himself acquainted, by actual observation, with any of the genera 

 to which he alludes. On page 2 38 of the second edition of Gegenbaur's ' Grundzuge,' 

 a somewhat awkwardly introduced reference to Dorner's paper on Branchiobdella 

 might lead an unwary reader to suppose that the statements there given, on the 

 authority of Kupffer and Leydig, with reference to the proliferation of blood-corpuscles 

 from the valves of the vessels in other leeches (Piscicola and Clepsine), have reference 

 to Branchiobdella — which they have not. A glance at Dorner's excellent memoir on 

 Branchiobdella would, however, suffice to satisfy a conscientious bookmaker that the 

 vascular fluid of Branchiobdella has not yet been shown to contain corpuscles, and 

 that it notoriously differs from the vascular fluid of true leeches, in that it most 

 certainly does not ' communicate with the perivisceral cavity so as to form a lacunar 

 circulation.' The introduction of Branchiobdella into the list given by Dr. George 

 Eolleston is, it would seem, due to his having misunderstood the German authors. 

 The statement that * the pseud-haemal system communicates with the perivisceral 

 cavity so as to form a lacunar circulation in Syllidea, the Opheliae, the Cirratulida, 

 and the Staurocephali ' is more difficult to account for than is that relation to Branchi- 

 obdella, since, whilst there is here no foundation whatever for such a statement in 

 fact, the description and figures of Claparede with reference to two at least of these 

 genera are admirable in clearness and detail. We are driven to the conclusion that 

 Dr. George Rolleston has acquainted himself with the introduction without having 

 consulted the body of Claparede's work. . . . Whilst I regret to find myself unable to 

 accede to the statements in the text-book which I have quoted above, I may point out 

 ' that the errors therein contained are not traceable to any attempt on the author's part 

 to make original observations in the domain of morphology, but are rather due to a 

 failure to observe accurately the contents of books.' It will be observed that while 

 some of these statements relate to matters of fact, and others to matters of inference 

 based upon facts, or supposed facts, a third set consists mostly of expressions of 

 Professor Lankester 's personal opinions. I shall deal only with the two former sets of 

 statements. 



