THE BLOOD-CORPUSCLES OF THE ANNELIDES. 491 



words, which state a positive fact, do not bear out Professor Lan- 

 kester's suggestion of the negative conclusion proverbially, and here 

 so specially, hard to prove. For, as regards the blood- vascular 

 system of the leeches generally, Leuckart, who includes under them 

 Branchiobdella, says (1. c. p. 670) : — ' The blood of the Hirudineae 

 contains exceedingly few blood corpuscles, and these, it should be 

 noted, do not, as it appears, even circulate in' every part of the 

 vascular apparatus.' Leuckart then proceeds to describe the various 

 bodies which go by the name of blood-corpuscles in the leeches, 

 with which animals he always classes Branchiobdella, and of the 

 vascular system of which animals he takes Branchiobcletta as a type 

 a few pages back. Similarly Leydig, who repeatedly refers to the 

 histology of Branchiobdella (e.g. 'Archiv fur Mikros. Anatomie/ i. 

 p. 274, 1865; ' Tafeln zur Vergleich. Anatomie, pi. ii. fig. 6), and 

 must repeatedly have had it, with its faintly- coloured blood, under 

 the microscope, as he tells us (' Zeitsch. Wiss. Zool.' i. p. 117, 1849) 

 he has had Piscicola, so like it in this respect, writes of the blood- 

 corpuscles of leeches without ever hinting that Branchiobdella (which 

 he, like Leuckart, considers to be one of the Hirudineae) differed 

 from them in this same cardinal point of the absence of corpuscles 

 from its vascular fluid. Both, then, of these excellent observers 

 consider Branchiobdella to be a leech ; both repeatedly treat of its 

 histology; both describe the blood-corpuscles of the Hirudineae; 

 neither ever suggests that these corpuscles are wanting to Branchiob- 

 della, though one of them, viz. Leydig ('Archiv Mikro. Anat.' I.e. 

 p. 281), does assert this of Chaetogaster, an animal, the somewhat 



authorities, into numerous small round non-nucleate bodies, which individually are 

 scarcely half the size of the nucleus of the cells, is the source of many, but not of all, 

 the smaller bodies visible in the blood of these animals. Retrograde, however, as well 

 as other changes, count for much of the ' Kornchenbildung ' of the blood as usually 

 examined, and good figures of such changes are given by Barry (' Phil. Trans.' 1840, 

 pi. xxix. fig. 6) and by Gulliver (Gerber's 'Anatomy,' fig. 268). The formation of 

 lymph corpuscles by proliferation of the peritoneal endothelium was demonstrated by 

 Schweigger-Seidel and Ludwig, in 1866, in Lud wig's 'Arbeiten' (i. 180). Kolliker 

 (• Gewebelehre,' p. 618, 1867) suggests that the like process may take place in the 

 smaller lymphatic vessels. Remak (' Untersuchungen uber Entwickelung,' p. 22) 

 made the same suggestion, in 1855, as to the blood-vessels, and Leydig, in 1857, in 

 his 'Histologie' (p. 447), has the following words: — 'Das sog. Gefassepithel scheint 

 ebenfalls durch Zellenwucherung die Zahi der Blutkugelchen vergrbssern oder die 

 etwas untergegangenen ersetzen zu kbnnen.' (See also ' Bau des Thierischen Korpers,' 

 1864, p. 67.) Dr. Beale, in his ■ Microscope in Medicine ' (1878, p. 252), pronounces 

 himself to the same effect. 



