PLASMODROMATA AND SARCODINA 



Wenyon did not see the cysts burst and the amoebae escape. 



Wenyon says : * When we take into account the striking similarity of these 

 two amoebae (L. muris and L. coli), both in the free condition and in their encyst- 

 ing process, it is difficult to avoid the conclusion that they are identical.' 



In 1 91 7 Wenyon and O'Connor published exceedingly valuable 

 researches on the diagnosis of L. coli and on the house-fly as a 

 carrier of the cysts. 



We therefore see that while a great deal is known as to the 

 structure, life-history, and method of infection, there is still much 

 to be observed. Are Schaudinn and Wenyon correct in their 

 description of autogamy, or does L. coli really form gametes like 

 Entamoeba hlattce ? Is there any true schizogony ? 



After this rather long history, we will not enter fully into the 

 structure of L.coli, but will only present a very condensed account. 



Morphology. — In diameter it measures as a rule 20 to 40 ^, 

 although forms as small as 10 [jl and even 5 [jl have been described. 

 The cytoplasm is vacuolated and contains bacteria, and extremely 

 rarely one red corpuscle. The ectoplasm is not visible until a 

 pseudopodium is about to be protruded. The vesicular nucleus 

 resembles that of the tetragena stage of L. histolytica, an account 

 of which is given below, but the cyclic changes are not so well 

 defined. The karyosome when present is small, and is composed 

 of two chromidia united by a chromatic substance. At the com- 

 mencement of a cycle this karyosome is a round compact mass of 

 chromatin connected with the periphery by a linin network with 

 few chromatinic granules. This karyosome breaks up, its chromatin 

 increasing in amount, the linin network becomes thicker, and 

 there are more chromatin granules at its nodes, and this goes 

 on until all the chromatin is collected as blocks under the nuclear 

 membrane and only a small granule is left in the centre, and then 

 the cycle begins again by the growth of the granule into a large 

 karyosome. 



Life-History. — The life-cycle comprises two phases: a binary 

 division by promitosis takes place (and not by amitosis, as de- 

 scribed by Schaudinn). The process of schizogony is described to 

 take place by repeated division into two, forming two, four, and 

 eight nuclei {vide Fig. 42, p. 292), which form eight little Loeschiae 

 which begin the asexual cycle again, but this is very doubtful. 

 Encystment takes place, followed by division of the nucleus into 

 two, four, and finally eight nuclei. During this stage a large 

 vacuole exists in the cytoplasm, which disappears in the eight- 

 nuclei stage. Contrary to Schaudinn, Hartmann and Whit more 

 believe that no zygosis takes place in the cyst, but that eight 

 little amoebae are formed which, on escaping from the cyst, they 

 think may conjugate in pairs and form the synkaryon or zygote 

 from which the vegetative forms arise after the manner described 

 by Mercier in 1909 for E. hlattce. Sometimes the cysts have more 

 than eight nuclei^ — e.g., ten or twelve — which must be considered 

 to be abnormal, 



