ZOOLOGY AND BOTANY, MICKOSCOPY, ETC, 



245 



tion. Indeed, if the ganglion be amputated with the siphon it will be 

 regenerated. Extirpation of the ganglion has two main effects : (a) an 

 interruption of co-ordination between the siphons, and (b) a reduction 

 of tone and general irritability of the animal. The ganglion regenerates 

 in four to six weeks. The new one is very quickly fatigued. An 

 account is given of responses to chemical stimulation. Both siphons are 

 sensitive to disturbing vibration. Amputated incurrent siphons respond 

 only if they are cut off. to include the circlet of tentacles ; amputated 

 excurrent siphons are insensitive ; deganglionate animals respond with 

 closure of both siphons, but a more vigorous stimulation than normal is 

 needed to elicit the response. A useful summary is given of the results 

 of previous investigators. The ganglion consists of a central fibrillar 

 substance surrounded by a peripheral layer of cells ; it develops from the 

 larval cerebral vesicle ; it is regenerated from a derivative of the same 

 tissue as that from which the original ganglion developed. The ganglion 

 of Ciona regalates reflexes in a feeble way either by inhibiting or facili- 

 tating them. J. A. T. 



Taxonomic Study of Salpidse. — Maynaed M. Metgalf (Bulletin 

 U.S. Nat. Museum, lOlS, 100, 5-193, 14 pis., 150 figs.). This is a 

 big piece of work, in which the author was assisted by Mary M. Bell. 

 In studying the inter-relationships the greatest significance attaches to 



Oblique vertical section of dorsal eye of Pegea confederata, sub- 

 species hicaudata, aggregated form, x 180. 



e'., basal portion of eye ; /c. , ectodermal epitbelium ; o.«., optic nerve ; 

 w.j.nerve leaving ganglion ; p., pigment; o.c, optic chamber, a lymph 

 space. 



the gut, the nervous system^ and the muscles, the symmetry or asymmetry 

 of the body and its muscles being also of some importance. The solitary 

 form is the more conservative ; the aggregated individuals are more 

 ])lastic and divergent. Some features of the secondarily simplified 

 nervous system are very inconstant, such as the number of nerves 

 radiating from the ganglion. The eyes of the aggregated form are 

 important taxonomically. Adaptive divergence and convergence can 



