418 KE. W. MACBRIDE. 
explains away the striking Chordate features presented by gill- 
sacs and nerve-cord, and founds a new theory on such a basis 
as I have just mentioned, can hardly expect to have much 
weight attached to his judgment. 
In conclusion I may be allowed to express my regret that 
Professor Spengel has not condensed his work more. The 
amount of apparently needless repetition is very great, which 
is all the more to be regretted as the amount of literature 
which every zoologist must read is immense and daily growing. 
Those who believe in the Chordate affinities of Balano- 
glossus will, however, derive consolation from the fact that in 
the huge volume we have been considering, every possible 
argument has been urged against this theory, and that, not- 
withstanding the great industry and ability which Professor 
Spengel has displayed in attacking it, all his attempts to shake 
it have, in my mind, signally failed. 
ZooLoGIcAL LABORATORY, CAMBRIDGE ; 
May 3rd, 1894. 
EXPLANATION OF PLATES 29 & 30, 
Illustrating Mr. E. W. Macbride’s Review of Professor 
Spengel’s Monograph on Balanoglossus. 
List oF ABBREVIATIONS USED. 
Al. Alimentary canal. 4/. Br. Dorsal branchial region of the alimentary 
canal. A/. @. Ventral esophageal region of the alimentary canal. Br. Branchial 
sac. Br. in., Br. ex. Internal and external openings of the samee Br. sk. 1. 
Skeletal rod in primary gill-bar or gill-septum. Br. sk. 2. Skeletal rod in 
secondary gill-bar or “ tongue-bar.” Bwcee. Buccal cavity or pharynx. C. 
Collar. ©. cw. Collar celom. Ch. Notochord. Ch}. Primary cuticular 
sheath of the same. Ch?. Secondary mesoblastic sheath of the same. @. NV. 
Central nervous system. C.p. Collar-pore. D. NV. Dorsal nerve-cord of 
trunk. D. R. Dorsal roots of central nervous system. D. V. Dorsal blood- - 
vessel. Zp.Br. Epibranchial epithelial band. G/. Glomerulus. Gox. Gonad. 
