AVERS. 



[Vol. VI. 



B. Morphological. 



"Die ausserordentliche Mannichfaltigkeit in der Bildung der Grundform erklart 

 sich bei den Organen ebenso wie bei den Plastiden daraus, dass die Anpassungs- 

 Verhaltnisse dieser morphologischen Individualitat absolut mannichfaltig sind, und 

 dass keine Schranke die Ausbildung des Organs wie der Plastide nach den verschie- 

 densten Richtungen behindert. Dazu kommt noch, dass die verwickelte Zusammen- 

 setzung der hohern Organe aus Complexen von niederen, die hochst complicirte 

 Verflechtung von Zellfusionen, einfachen Organen, zusammengesetzten Organen, 

 Organ-Systemen und Organ-Apparaten, alle mriglichen Grundformen zu verwirklichen 

 im Stande ist." — Haeckel, Gejierelle Alorphologie, II. 531. 



1. Stage of the cell colony. 



2. Stage of the simple or 

 homoplastic organ. 



3. Stage of the compound 

 or heteroplastic organ. 



4. Stage of the organ sys- 

 tem. 



5. Stage of the organ ap- 

 paratus. 



Auditory Organology. 



simplest condition and earliest phase of a group of ecto- 

 derm cells transformed to sensory cells. 



recognized by its sharp differentiation from surround- 

 ing tissue. The surface sense organ. 



recognized by the division and protection of the organs 

 in canals below the surface. 



the phase in which the canal complex, although com- 

 plicated, remains independent as the functional ear. 



the phase in which the canal complex acquires anatom- 

 ical and physiological relations with other very dif- 

 ferent structures {e.g. the middle and outer ear of 

 higher vertebrates) and with them performs the 

 auditory function. 



A description of the internal ear of the Sting Ray {Dasyatis 

 centrurus), with comparative accounts of the internal ears of 

 the Electric Ray {Torpedo occidentalis), the Hagfish {Myxine 

 glutinosa), the Lamper Eel {Petromyzon mariims), the Alligator 

 {A. mississippiensis), the Mocking-bird {Mimus polygloUus), and 

 of Man. 



1. Canals. 



2. Endolymphatic duct. 



3. Maculae. 



4. Utriculus. 



5. Sacculus. 



6. Lagena (cochlea), of the ichthyopsida and sauropsida 



7. Tectorial membranes and cupulse terminales. 



8. Otoliths otoconie. 



9. Perilymphatic spaces of the ear. 



10. Continuity of the cerebral and auditory spaces. 



11. Mammalian cochlea. 



12. Auditory nerve. 



