14 TUBIFEX KIVULORUM. 



For the examination of the Protein-Crystals or Crystalloids of 

 the tuber of the potato, the skin of the tuber should first be re- 

 moved and a very thin section then taken parallel to the surface. 

 The Crystalloids are not present in all potato-tubers, nor are they 

 equally developed in all those in which they exist ; but in cells 

 containing them, they may generally be found either embedded in 

 the protoplasm, often in the immediate neighbourhood of the 

 nucleus, or in contact with the primordial utricle. They are also 

 to be found in many oily seeds, such as the Brazil nut, the Castor- 

 oil seed, the Hazel nut, etc., where they lie embedded among the 

 other granular contents of the cells, and may be brought into view 

 by cutting thin sections through the endosperm. 



®n ^ubifey IRivulorum. 



By a. Hammond, F.L.S. 



Plate I. 



THE following observations on the structure of this inter- 

 esting little worm are the result of such study of the 

 subject as the author has been able to make during the 

 short period of about eight weeks. They, therefore, must not 

 be taken as either exhausting the subject, or as offering any new 

 information thereupon. To tell, indeed, all that might be said 

 upon it would require far more space than can probably be 

 spared for it in the pages of our newly-started Journal. 



A reddish blush, spread over the surface of the mud at the 

 margin of a slowly-moving stream, is a sure indication of the 

 presence of Tubifex ; touch the surface, however lightly, with the 

 end of your stick, and the blush disappears for some inches 

 around it, showing the extreme sensibility of the sense of touch 

 in these animals, as in others of their class — a sensibility, indeed, 

 which supplies the place of all other organs of perception. The 

 name " Tubifex" was applied to these worms by Lamark, from the 

 habit they are said to have of constructing a muddy or sandy tube 

 for their dwelling, in which they reside head downwards, the tail 

 projecting from the orifice, and waving to and fro in the water for 

 the purpose of respiration. It is somewhat singular, that 1 have 

 frequently obtained a plentiful supply of worms without a single 

 fragment of the tubes ; at other times, I have obtained the tubes, 

 but in small numbers, totally disproportionate to those of the 

 worms ; and on such occasions, my finding of them has been 

 associated with two curious circumstances. First, that the tubes 



