. Comparative anatomy. Anatomy, Comparative. SOLENOCYTES ...DORSAL fAORTA CAPILLARY, — PROTONEPHRIDIUM PHARYNX PERI BRANCHIAL. 'NEPHROPORE Fig. 331.—Diagrams of the protonephridia of Amphioxus. A is a section in the pharyngeal region—through a gill septum on the left and through a gill slit on the right. B is an enlarged section of a protonephridium showing the attached solenocytes. Such a protonephridium is practically identical in structure with a protonephridium of annelids. (Redrawn after Boveri and Goodrich.) porting the assumption that chordates have an annelid ancestry. It seems more li
. Comparative anatomy. Anatomy, Comparative. SOLENOCYTES ...DORSAL fAORTA CAPILLARY, — PROTONEPHRIDIUM PHARYNX PERI BRANCHIAL. 'NEPHROPORE Fig. 331.—Diagrams of the protonephridia of Amphioxus. A is a section in the pharyngeal region—through a gill septum on the left and through a gill slit on the right. B is an enlarged section of a protonephridium showing the attached solenocytes. Such a protonephridium is practically identical in structure with a protonephridium of annelids. (Redrawn after Boveri and Goodrich.) porting the assumption that chordates have an annelid ancestry. It seems more likely however that we have here another case of convergence. The nephridia of amphioxus are protonephridia associated with the secondary gill-arches. They are short branched tubules which open into the peribranchial cavity, sometimes as many as ninety pairs. The fact that they are ectodermal in origin and are limited to the gill-region, while the excretory tubules of vertebrates are mesodermal and postbranchial, is sufficient to show that the two are not homologous. That the nephridia of amphioxus are protonephridia comparable with those of annelids is evidenced by the fact that they are ectodermal and metamerically arranged and have their blind terminations beset with solenocytes almost identical in structure with those of annelids. Craniota. Three successive kidneys make their appearance in verte- brates, pronephroi, mesonephroi, and metanephroi. That the tubules of these three kidneys are comparable with coelomoducts is sufficiently. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Neal, Herbert V. (Herbert Vincent), 1869-1940; Rand, Herbert W. (Herbert Wilbur), 1872-1960. Philadelphia : P. Blakiston's Son
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