Protozoa Parasitic in Frogs, Part II. 347 



which remains at the front end of the body during movement, 

 hut it is only faintly visible in the living animal (Plate LXXT., Fig 

 1). When stained in picro-carmine it shows up very clearly and 

 is seen to be made up of a central dense granulated portion, a 

 clear homogeneous peripheral portion, and a nuclear membrane 

 closely investing the latter. It measures roughly 9/x, in dia- 

 meter. A conti'Hctile vacuole is sometimes visible (Plate LXXI.,Fig. 

 6). In some instances individuals obtained from the tadpoles 

 showed a very bright appearance owing to numerous green and 

 brown bodies present in the protoplasmic stream. These in- 

 clusions appeared to be algal spores, diatoms, desmids or their 

 cases, sand grains and other small pieces of debris. Although 

 these were present in large numbers, the amoebae seemed to 

 carry them along with great ease. Others again were found 

 containing colourless oily contents only. Those found living in 

 the frog never contained any green bodies, the protoplasm con- 

 sisting mainl}' of ordinary small food vacuoles. 



The protoplasm streams very rapidly and can be traced along 

 the middle of the bod}' to the anterior end and then back along 

 the sides, but not extending into the posterior region. 



When the amoeba is moving along, it always advances in a 

 definite direction with the larger anterior end foremost. It 

 assumes various shapes but retains as a whole a more or less 

 elongated form (Plate LXXI., Figs. 1. 2, 3, 4 and 5). In creeping 

 forwards a very slight bulging occurs at the front end, which 

 appears to be made of ectoplasm only, being quite free from the 

 larger granules. The protoplasm at once streams into this 

 portion, and the whole individual is thus drawn forward. The 

 contents stream so rapidly into the advancing portion that 

 generally there is no actual pseudopodium (ectoplasmic) visible. 

 The very front end of the amoeba appears to roll over gently 

 and smoothly in a forward direction, and this seems to extend the 

 animal slightly ; with this action and with the protoplasm 

 streaming ahead, the individual advances. Only occasionally 

 have I observed the clear portion of the ectoplasm remaining at 

 the front end where the protoplasm had not yet flowed into the 

 projecting pseudopodium, and this is the only time at which 

 ectosarc and endosarc are clearly separate. The direction of 

 movement is changed by the bulging or rolling motion taking 



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