GOLDSCHMIDT S MOXOGEAPH OF AMPHIOXIDES. 



589 



Their contraction occurs under stimulus, but, far from in- 

 ducing respiratory currents, it temporarily inhibits them. In 

 point of fact rhythmic muscular respiratory movements have 

 not been observed in Acraniata. 



The gill-arches of Amphioxides (fig. 3) possess the essen- 

 tial qualifications of a true vertebrate gill-arch, namely, the 

 endodermal pharyngeal epithelium; the ectodermal portion 

 of the body-wall ; the branchial coelom ; the branchial mus- 

 cles, which are true visceral muscles derived from the wall of 

 the ccelom. They appear, in the preserved material, to pro- 



FiG. 3. — Diagram representing the structure of tlie brancliial 

 ajjparatus of Amphioxides. The ventral half of tlie body with 

 the pars respiratoria has been exposed by a frontal incision. From 

 Goldschmidt. ksp. Gill-slit. kib. Gill-arch. mik. Median furrow 

 of gill-arch, ki.coe. Coelom of gill-arch. Coel. General ccelom. 

 b.w. Body-wall. 



ject into the pharynx like hollow sacs between the gill- 

 slits, each arch being apparently divided incompletely into 

 right and left compartments by a median groove, and the 

 suggestion is made that this bilateral disposition may be a 

 stage towards the duplication of the slits. The respiratory 

 epithelium is described as a many-layered ciliated epithe- 

 lium ; a similar appearance may be noted in other species, 

 but it has been shown, in the first place by Langerhans, that 



