[271] Vide Vol. II. p. 374; also Götte, Zool. Anzeiger, No. [80], p. 189.

[272] C. Grobben. “Die Entwick. d. Moina rectirostris.” Arbeit. a. d. zool. Instit. Wien. Vol. II. 1879.

[273] Balbiani (No. [554]) has also recently dealt with this subject, but I cannot bring my own observations into accord with his as to the structure of the Elasmobranch testis.

[274] An entirely different view of the origin of the sperm cells has been adopted by Balbiani, for which the reader is referred to his Memoir (No. [554]).

[275] For a summary of the facts on this subject vide Bronn, Klassen u. Ordnungen d. Thierreichs, Vol. III. p. 404.

[276] It would be interesting to have further information about Balanoglossus.

[277] These views fit in very well with those already put forward in Chapter XIII. on the affinities of the Echinodermata.

CHAPTER XXV.

THE ALIMENTARY CANAL AND ITS APPENDAGES, IN THE CHORDATA.