PROGRESS OF MICROSCOPICAL SCIENCE. 233 



published in 1870, as stated by M. Agassiz, but tbe evidence was not 

 conclusive, for tbe complete development and metamorphosis had not 

 been observed. It is, therefore, very gratifying to have this impor- 

 tant point settled so soon and so satisfactorily. M. Agassiz gives an 

 excellent account of the structure, both of the larva in its various 

 stages and of the adult Balanoglossus, and discusses their relations to 

 other worms. He concludes that when, at last, the true structure of 

 tbis remarkable larva and its history have been ascertained, its true 

 relations to the larvae of Annelids are sufficiently clear, while tbe re- 

 lations to Echinoderm larvae are not so close as bad been supposed, 

 for the parts are not homologous with those of the latter, although the 

 external resemblance is quite remarkable. Nor does he admit that 

 this worm, either by its structure or mode of development, can be 

 regarded as connecting the Annelids and Echinoderms. " It is un- 

 doubtedly the strongest case which could be taken to prove their iden- 

 tity ; but when we come carefully to analyze the anatomy of true 

 Echinoderm larvae, and compare it with tbat of Tornaria, we find that 

 we leave as wide a gulf as ever between the structure of the Echino- 

 derms and that of the Annuloids." The plates are excellent, and 

 illustrate well both the external appearance and anatomy of the Tor- 

 naria stage, the young Balanoglossus, and the adult. This worm is oi 

 large size when mature, and lives in the sand at low-water mark. It 

 occurs on the sandy shores of southern New England and southward ; 

 M. Agassiz has found it at Beverly, Mass., as well as on the shores 

 of Vineyard Sound and at Newport. The writer also has specimens 

 from Naushon Island. M. Agassiz does not mention, and therefore 

 has doubtless overlooked the fact, that Mr. Chas. Girard, just twenty 

 years ago, described a species of Balanoglossus from South Carolina, 

 under the name of Stimpsonia aurantiaca. It is true that Girard's 

 description was quite imperfect, like all the early descriptions of 

 tbis singular genus, but no one can doubt that his species was a 

 Balanoglossus, and judging from the description, it is most likely 

 identical with tbe B. KowalevsJcii, so well described and illustrated 

 by M. Agassiz in the memoir before us. 



Histology of the Tympanum. — Mr. John C. Galton, M.A., says in a 

 late number of the ' Medical Record,' tbat Dr. Riidinger, Prosector in 

 the Institute of Anatomy, at Munich, has just published some contri- 

 butions towards the Minute Anatomy of the Tympanic Cavity (Beitrcige 

 zur Histologie des Mittleren Ohres), illustrated by twelve lithographic 

 plates, each containing, on an average, two large figures. Six chapters 

 deal respectively with the following subjects : — 1. Osseous substance 

 and medullary cavity of the auditory ossicles. 2. The annulus carti- 

 lagineus and membrana propria, with their relation to the malleus. 

 3. The processus brevis of tbe malleus, and its relation to the tym- 

 panic membrane. 4. The folds (Taschenbander) of the tympanic mem- 

 brane, with relation to the malleus. 5. The lodgment of the tympanic 

 membrane in the sulcus tympanicus. 6. Additional observations on 

 the articulation between the auditory ossicles. The chapters are 

 rather short, but in these due reference is made to the published works 

 of previous observers, among which the beautifully illustrated mono- 



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