Generative organs, pp. [741]-748. Porifera, p. [741]. Cœlenterata, pp. [741]-743. Chætopoda and Gephyrea, p. [743]. Chætognatha, pp. [743]-745. Polyzoa, p. [745] Nematoda, p. [745]. Insecta, p. [745]. Crustacea, pp. [745], [746]. Chordata, pp. [746]-748. Bibliography of generative organs, p. [748]. Genital ducts, pp. [748]-753.
Chapter XXV. The Alimentary Canal and its appendages in the Chordata. Pp. [754]-780.
Mesenteron, pp. [754]-774. Subnotochordal rod, pp. [754]-756. Splanchnic mesoblast and mesentery, pp. [756]-758. Respiratory division of the Mesenteron, pp. [758]-766. Thyroid body, pp. [759]-762. Thymus gland, pp. [762], [763]. Swimming bladder and lungs, pp. [763]-766, The middle division of the Mesenteron, pp. [766]-771. Cloaca, pp. [766], [767]. Intestine, pp. [767], [768]. Liver, pp. [769], [770]. Pancreas, pp. [770], [771]. Postanal section of the Mesenteron, pp. [771]-774.
The stomodæum, pp. [774]-778. Comparative development of oral cavity, pp. [774]-776. Teeth, pp. [776]-778.
The proctodæum, pp. [778]-780. Bibliography of alimentary canal, p. [780].
EMBRYOLOGY.
CHAPTER I.
CEPHALOCHORDA.
The developmental history of the Chordata has been studied far more completely than that of any of the groups so far considered; and the results which have been arrived at are of striking interest and importance. Three main subdivisions of this group can be recognized: (1) the Cephalochorda containing the single genus Amphioxus; (2) the Urochorda or Tunicata; and (3) the Vertebrata[1]. The members of the second and probably of the first of these groups have undergone degeneration, but at the same time the members of the first group especially undergo a less modified development than that of other Chordata.