456 Dr. G. C. Wallich on the Distinctive Characters, Habits, 



of sarcode, but not till it has become consolidated to a certain 

 extent ; and this consolidation does not take place within the 

 substance, but only at the surface. If we take the example of 

 an ordinary contractile substance, the process is to all intents the 

 same. Thus caoutchouc, when oozing from the parent tree, is 

 not contractile, but a semifluid adhesive mass. So is the 

 sarcode of the interior of an Amoeha. But as soon as the action 

 of the atmosphere causes coagulation or consolidation of the 

 caoutchouc tears, the innate contractility becomes at once 

 manifest. A precisely similar effect is produced by the contact 

 between the endosarc and water. 



, It is quite evident that in the case of caoutchouc, the con- 

 solidation once produced, there is no return to the previous 

 condition. Why? simply because its vitality ceased with its 

 extrusion. But even here the analogy is not altogether de- 

 stroyed ; for the contractility of the caoutchouc may be materially 

 diminished by heat, and it may again become an adhesive 

 semifluid mass, capable of permanently assuming any figure. 

 Yet, on reduction of the temperature, again consolidation takes 

 place, and with it the mass resumes its elasticity. So that, 

 assuming sarcode to be endowed with vitality — a fact, I presume, 

 not admitting of denial — and also that it is contractile, we have 

 not only all the conditions that place the phenomena observed 

 in the light of simple cause and eff^ect, but it appears to me 

 obviously impossible to account for them in any other rational 

 way. 



In the ' Annals ' for June (p. 451) a cursory allusion was made 

 to two varieties of the common Difflugia proteiformis, which were 

 present in the Hampstead pools. These varieties afforded good 

 illustrations of the tendency of the test to undergo considerable 

 modifications in shape and likewise in the disposition of the 

 extraneously derived materials of which it is for the most part 

 built up. It was stated that whereas the basal substance, with 

 which the sandy particles commonly present in the test are 

 cemented together, is secreted by, or, to speak more correctly, is 

 an exudation from, the animal, examples are frequently met with 

 in which there is no readily appreciable intermixture of mineral 

 particles, and the entire test would seem to be composed of 

 almost colourless pellets, differing only from those seen in the 

 tubes of Melicerta in their shape and freedom from colouring 

 matters. These pellets are minute cylinders having rounded 

 ends. They are occasionally straight, occasionally more or less 

 curved, and vary in length from 5000^^ ^^ 3cm5o^^ ^^ ^^ inch, 

 whilst their diameter varies from 20000^^ ^^ 10000^^ °^ ^^ inch. 

 They are distributed over the surface in a single layer, the larger 

 and smaller pellets being made to fit to each other. Some 



