rUOTOZOA OF HERTFORDSniRE. 121 



genus Eitfodininm is, I believe, confined to the stomachal cavity of 

 cows. Hcrpdomonas Lewiu has been recently discovered in the 

 blood of healthy rats. Trypanosoma is found in the rectum of 

 poultry. Balantidinm coli even honours the human subject with 

 its presence. The Infusoria are to be found in enormous numbers 

 in dew, and indeed their presence may be said to be universal. 



The animalcules which are now to be brought before your notice 

 have been found in the neighbourhood by myself or other members 

 of the Society. 



The order Amcebiiva is the first of the six orders which compose 

 the class Khizopoda. 



Amoeba proteus is the starting-point in the animal kingdom ; it 

 appears to be the simple parent stock from which all the Protozoa 

 have been evolved. It may be described as a simple mass of jelly- 

 like sarcode, or protoplasm, having no definite form, its outline 

 being as changeable as that of the fabled Proteus, from which 

 it takes its name. It simply creeps through the water by means of 

 lobate projections or pseudopodia (false feet), which are protruded 

 indiiferently from any part of the body, incepting its food by 

 rolling over it and wrapping it up, as it were, within its body. 

 This is the commonest type of the Rhizopoda, and is to be found 

 everywhere, especially where decaying vegetable matter exists. 



Advancing a step, we come to the Gkegaeinida, curious animal- 

 parasites, consisting of a simple cell, usually of an ovate form. 

 These mostly inhabit the intestines of the earth-worm and the larvae 

 of insects — a field which up to the present time I have not exploi-ed, 

 and I cannot, therefore, report upon them. 



The next order is the Arcellinida. Here we have amoebiform 

 rhizopods, inhabiting a shell or test. Of this order I have found 

 five representatives. The first is Gromia oviformis. This animalcule 

 inhabits an egg-shaped brownish envelope, about 1-1 0th of an inch 

 in length, which has a single round orifice, from which the proto- 

 plasm streams forth, ramifies, and inosculates until a network is 

 formed, and when any minute protophyte or food-substance is 

 entrapped the pseudopodia are withdrawn into the interior, and the 

 nutritive substance assimilated. Gromia creeps about by means of 

 these pseudopodia. The next I have found is Arcella vulgaris. 

 Here the shell or test is circular, of a horny nature, and of a 

 bright chestnut hue, bearing markings resembling the engine- 

 turning at the back of a watch. These two were found in Ball's 

 Park ; the latter is very common. Another less common species is 

 Arcella aculeata, the test of which is furnished with peculiar curved 

 spines. 



Other examples of this order are Biffltigia ohlonga and Bifflugia 

 proteiformis, in which the test is made up of very minute sand- 

 grains cemented together. The pseudopodia in this genus and in 

 Arcella are short and lobate, not often exceeding the length of the 

 body, thus differing from Gromia, where they are very fine and 

 spread out to about four times the length of the body. 



