biological study op tap water. 421 



Protozoa. 



The animal forms belong mostly to the Protozoa, being nearly all 

 included in the groups Rhizopoda and Flagellate Infusoria. 



Rhizopoda. — Among the Phizopods were noticed at least two 

 species of Amoeba — A. proteus and A. radiosa, but not very fre- 

 quently ; on several occasions also Difflugia globulosa, Actinophry s 

 sol, and Acanthocystis turf area {sp ?). 



Flagellata — Belonging to the Flagellata Infusoria there are a few 

 interesting forms, some of which I shall notice in detail. 



Monas lens is occasionally seen, but by far the commonest species 

 is Dinobryon sertularia, and a brief description of this beautiful 

 animalcule will not be out of place. In the spring and early summer 

 they are to be found in large numbers in every filtering, but in 

 autumn and through the winter they are rarely met with. 



In the classification adopted by W. Saville Kent, in his " Manual 

 of the Infusoria," they are placed in the Order Flagellata Fustomata, 

 and Family Chrysomonadidae. The characters of the order are as 

 follows : " Animalcules possessing one or more fiagelliform append- 

 ages, but no locomotive organs in the form of cilia ; a distinct oral 

 aperture or cytostome invariably developed ; multiplying by longi- 

 tudinal or transverse fission, or by subdivision of the whole or part 

 of the body-substance into sporular elements ;" and of the family : 

 " Animalcules bi-flagellate, rarely niono-flagellate, social or solitary, 

 free-swimming or adherent, naked, loricate, or immersed within a 

 common mucilaginous matrix or zoocytium ; endoplasm always con- 

 taining two lateral, occasionally green, but more usually olive-brown 

 or yellow differentiated pigment bands ; one or more supplementary 

 eye-like pigment spots frequently present," and, as far as at present 

 known, they all inhabit fresh water. 



The genus Dinobryon consists of animalcules with two flagella, 

 one considerably longer than the other • attached by a contractile 

 ligament to the bottom of a colorless horny lorica, the individual 

 loricae being connected together so as to form a colony or compound 

 branching polythecium ; endoplasm containing two lateral green 

 bands, and a conspicuous eye-like pigment spot situated anteriorly. 



In the species D. sertularia Ehr. the individual loricae are per- 

 fectly hygaline and transparent, and are shaped in general like an 



