10 1 8 The American Naturalist. [November 
ton. He finds that the true teeth are functional for a considerable 
part of the animal's existence, cutting the gum as usual, and, after be- 
ing worn down by friction with food and sand, are shed from the 
mouth as are the milk teeth of other animals. The later cornules, or 
horny teeth, are certainly developed from the epithelium of the mouth 
cavity ; but from that under and around instead of over the teeth, and 
the hollows in the horny plates are the vestiges of the original alveoli of 
the teeth, from out of which the latter have been shed. A result of 
this discovery is that we now have perfect calcified teeth large enough 
to be studied with the naked eye, and hence available for comparison 
with other forms. Mr. Thomas, aided by Lydekker and Boulenger, 
fails to find any teeth of recent or fossil reptiles or mammals which 
quite correspond to those of Ornithorhynchus. He is more and more 
inclined to believe in the correctness of the view of Prof. E. D. Cope, 
that the Multituberculata v.ere monotremes, although the resemblances 
between the teeth are of the most general character. — J. S. K. 
Zoological News.— Sponges.— The third and fourth part of 
the 48th volume of the Zeitschrifi fiir ivissenschaftliche Zoologie is de- 
voted entirely to sponges. Conrad Keller devotes 95 pages and six 
plates to the sponge fauna of the Red Sea, and R. von Lendenfeld 
296 pages and 15 plates to the physiology of these forms. His exper- 
iments consisted in feeding these forms carmine, starch, and milk, and 
in trying the effects of various poisons upon them. Among the con- 
clusions are the following : The collar-cells absorb all that comes to 
them, holding the good and rejecting the useless. The canal system 
is physiologically comparable to that of polyps and medusse, while 
physiologically the sponges are the closest of all animals to the plants. 
Worms.- Arthur E. Shipley describes (Proc. Roy. Soc, No. 280) 
the structure of the Bahaman Gephyrean, Phymosoma varians. The 
points elucidated are the existence of skeletal structures at the anterior 
end of the body serving to support the tentacles and giving insertion 
to the retractor muscles; the alimentary canal; vascular system; 
nephridia, nervous system, sense organs, and reproductive organs. He 
thinks the points found confirm the arrangement of Phoronis near the 
Ciephyrea in Ermis. 
Vertebrates.— J. Beard has a preliminary notice of the early de- 
velopment of Lepidosteus osseus in the Proceedings of the Royal 
Society, No. 280. He obtained his material in northern New York. 
Among the points obtained are these : There is no neurenteric canal. 
