,8,,. NOTES AND COMMENTS. 491 



line " in fishes. Not only so, but it is pointed out that the super- 

 ficial slime-canal itself actually remains in distorted fragments in the 

 perfected ear. The semi-circular canals, according to Dr. Ayers, are 

 " simply remnants of the canal system of the surface," and " have no 

 active part in the auditory function. They serve merely as chambers 

 to hold the liquid necessary to float the auditory sensory hairs." The 

 "otoliths in the ear chambers are to be considered as essentially 

 foreign bodies . . . the result of the secretive action of the 

 ectoderm cells, which in ancestral forms produce the surface scales. 

 The higher we rise in the vertebrate series, and also the greater the 

 auditory sensitiveness, the fewer the otoliths found in the ear, . . ." 

 " The functions of the ampullar sense organs and their connected 

 canals can hardly be different from the sense organs of the lateral 

 line, except in refinement of function ; i.e., the difference can only be 

 one of degree, and not of kind." Moreover, " in Elasmobranchs, the 

 structural connection between the ear organs and the surface canal 

 organs is for a long time maintained." 



In conclusion. Dr. Ayers maintains that the organ of hearing in 

 Invertebrata is totally distinct from that of the Vertebrata, and he 

 combats the views of Retzius, who supposes that there is a funda- 

 mental difference between the ear of a lamprey and that of an ordinary 

 fish. Dr. Beard is also much criticised. 



Vanilla Disease in the Seychelles. 



The large and widely-distributed family of Orchids, though much 

 in favour with horticulturists, is one of the most useless from 

 an economic point of view. One genus forms an exception — 

 practically the only exception ; it has given its name to the product 

 for which it is known. The genus Vanilla contains about twenty 

 species widely distributed throughout the tropics. The plants are 

 terrestrial and herbaceous, but tall, sturdy climbers, with leathery or 

 fleshy leaves, and bear racemes or spikes of large though usually 

 dull-coloured flowers. The fruit or capsule, which is often elongated 

 and fleshy, with the appearance of a pod, is very generally used for 

 flavouring chocolate, liqueurs, &c. The best product is obtained from 

 a Mexican species, Vanilla plani folia, which is extensively cultivated 

 in other parts of the tropics. 



In recent years, the cultivation of Vanilla has been taken up in 

 the Seychelles, and a considerable industry established. Unfortu- 

 nately, however, this has been threatened by the appearance of a 

 disease which, in some areas, has led to much loss, as it affects the 

 pods, causing them to turn black, and fall before ripening. In 1887, 

 material sent from the islands to Kew was examined by Mr. George 

 Massee, but owing to bad packing proved useless for investigation. 

 In February, 1890, a second consignment was received representing 

 every stage of the disease, and conclusively showing that it is caused 



