THE BLOOD-CORPUSCLES OF THE ANNELIDES. 485 



that of the presence of their hosts. (See Professor Klebs, 'Vortrag 

 uber die Umgestaltung der Medicinischen Anschauungen,' 1878, 

 pp. 52-53, as regards Lepra.) It finds no place in the ■ British 

 Museum Catalogue of Worms,' by Dr. Geoge Johnston, 1865, nor 

 in Mr. Edward Parfitt's ' Catalogue of the Annelides of Devon,' 

 published in 1878 ('Trans. Devon Assoc. Science, Literature, and 

 Art'). Mr. W. H. Jackson, Demonstrator of Anatomy in the 

 Oxford University Museum, has often looked for it upon the 

 numerous Astaci which are dissected here every term under his 

 guidance, but in vain. I myself, and others elsewhere, have been 

 equally unsuccessful ; and though our examinations of the gills have 

 been often rewarded by the sight of the beautiful Cothurnia Astaci, 

 I doubt whether it has been the good-fortune of other investigators 

 to meet with this animal, apparently so common on the Continent, 

 within our four seas, or at any rate in these southern counties. 

 Hence I have been obliged to content myself with the plates and 

 descriptions given by Odier and Henle (loc. eit); by Keferstein 

 ('Archiv Anat. und Phys.' 1863, p. 509); by Dr. Dorner (loc. cit.); 

 and, above all, with the statements of Leuckart and Leydig re- 

 lating to it, the omission of the two latter of which names from 

 a list of the authorities upon this subject appearing to me to be 

 about as singular a proceeding as would be the omission of the 

 names of Podalirius and Machaon from a list of the doctors in the 

 Iliad. Inaccessible though the animal has been to me in the 

 fresh state, and though the difficulties besetting much of its anatomy 

 are such as to make it more than ordinarily hard to prove a posi- 

 tive, not to say a negative, conclusion respecting it, the animal 

 nevertheless possesses very considerable claims upon the attentive 

 consideration of the classificatory zootomist, being, as it is, an an- 

 nectent form between the Hirudineae and the Oligochaeta. And as the 

 peculiarities of its structural arrangements are specially interesting 

 to those who, like myself (see note, p. 138, 'Forms of Animal 

 Life '), would unite the two families together with the Polychaeta 

 under the common term ' Annelides,' as a class name 1 , a glance at 



1 The question as to the propriety of ranging the Hirudineae or Discophora in the 

 same class even with the Chaetophora has been perpetually raised even down to 

 entirely recent times. Grube, in his excellent memoir on ' Die Familien des Anneliden ' 

 (Wiegmann's 'Archiv,' 1850, S.A. p. 1), writes thus : — 'Ein jeder, der von Anneliden 

 handelt, eine Erklarung schuldig, ob er sie in dem Sinne von Cuvier, von Milne 



