(359) O. Bütschli. “Entwicklungsgeschichtliche Beiträge (Nephelis).” Zeit. f. wiss. Zool. Vol. XXIX. 1877.
(360) E. Grube. Untersuchungen üb. d. Entwicklung d. Anneliden. Königsberg, 1844.
(361) C. K. Hoffmann. “Zur Entwicklungsgeschichte d. Clepsineen.” Niederländ. Archiv f. Zool. Vol. IV. 1877.
(362) R. Leuckart. Die menschlichen Parasiten (Hirudo), Vol. I. p. 686, et seq.
(363) H. Rathke. Beit. z. Entwicklungsgesch. d. Hirudineen. Leipzig, 1862.
(364) Ch. Robin. Mém. sur le Développement embryogenique des Hirudinées. Paris, 1875.
(365) C. O. Whitman. “Embryology of Clepsine.” Quart. J. of Micro. Science, Vol. XVIII. 1878.
[Vide also C. Semper (No. [355]) and Kowalevsky (No. [342]) for isolated observations.]
[143] The Discophora are divided into the following groups:
I. Rhyncobdellidæ.
II. Gnathobdellidæ.
III. Branchiobdellidæ.
[144] Hoffmann’s account (No. [36]) is so different from that of other observers that I have been unable to make any use of it.
[145] According to Robin it is more usual for there to be only a triple row of primary neuroblasts.
[146] Doubts have been cast by Whitman on the above account of the origin of the four epiblast cells.
[147] According to Robin this system of muscles becomes gradually strengthened and converted into the permanent system. Rathke on the other hand states that it is provisional, and that it is replaced by the muscles developed from the mesoblastic somites. It is possible to suppose that it may really become incorporated in the latter system.