480 cobb: further notes on tricoma 



and if either tridymite or cristobalite, formed under any condi- 

 tions, be kept in contact with a melt in which it is slightly sol- 

 uble, for a comparatively short time at a temperature below 

 870°, it will pass over into quartz, and no record will be left of 

 the previous existence of the higher form. 



The a-/3 inversions of each of the three minerals are of a dif- 

 ferent class. They take place immediately when the appropriate 

 temperature is passed in either direction, and the value of the 

 a-p inversion-point of quartz at 575° as establishing a point on 

 the geological thermometer, is left unchanged by the present 

 investigation. 



HELMINTHOLOGY.— Further notes on Tricoma. N. A. Cobb. 

 Communicated by F. V. Coville. 



In the years 1888 and 1889, while carrying on some investi- 

 gations at the zoological station at Naples, where thru the liber- 

 ality of the British Association for the Advancement of Science, 

 I had the use of one of its tables, I discovered a remarkable 

 nematode — so remarkable indeed, that competent helmintholo- 

 gists have repeatedly expressed doubt as to whether it is really 

 a nematode. 



Later a short note on this species was published in the Pro- 

 ceedings of the Linnean Society 1 (N. S. W.) under the title, Tricoma 

 and other New Nematode Genera, concluding with the words 

 "These few notes comprise all that is known concerning the 

 structure of a worm, which, were it less remarkable, I should 

 not notice at this writing." 



The note in the Proceedings was accompanied by two care- 

 fully drawn figures, one of the head and the other of the tail. 

 Unfortunately the only preserved specimen in existence at that 

 time was lost immediately after the drawings were made, so that 

 no further details were available. However, before the speci- 

 men was lost T had become thoroly satisfied that it was a nema- 

 tode of typical internal organization, but with an unusual devel- 

 opment of the cuticle. This development is so exceptional as 



1 Vol. viii (Series 2). October 25, 1893. 



