AiluUfi and Ova 117 



After detailed criticism of Sambon's argiiincnts, Looss 



ooss dismisses them with the conchision that *' in all the evidence 



„ \ there is not the slightest detail which would really point to 



o '' . the existence of a distinct species in the West Indies and 



certain parts of Africa." He adds that one of the fmida- 



mental facts on which his views rest is that in 1852 Bilharz actually found 



in Egypt that " the eggs of S. hcematohiiim and S. mansoni may occur in 



one and the same individual." 



„ ^. Keplying in 1909, Sambon [428] pertinently points out 



-D " that Bilharz's alleged observation has never been confirmed 



and that the interpretation that both lateral-spined and 

 terminal-spined eggs were actually seen in the same individual worm does 

 not necessarily follow from Bilharz's statement. In turn he attacks 

 Looss' hypothesis, especially his assmnption of the occurrence of partheno- 

 genesis in the adults. 



■p , The effectiveness of this criticism is revealed by the 



PiE ADJUSTMENT I'^adjustmcnt of his position by Looss in 1911 [298]. He 

 now recognized that " the question of the formation of 

 these eggs and the question of their fertilization are in reality independent." 

 He is still of opinion that the uncopulated females are incapable of giving 

 their eggs the normal shape. After fertilization the change to normal 

 shape will not take place immediately ; there will always be a transition 

 period. There is thus no longer any necessity of admitting on the part of 

 the egg cell a capability of developing by parthenogenesis." " I have 

 received the impression that when once the production of normal eggs 

 begins, the others are, as a rule, quickly evacuated." " That the females of 

 S. hcBmatohium can, and do, produce the two forms of eggs is beyond 

 question even now." 



American parasitologists attempted to settle the con- 

 YiA Media, troversy by suggesting that possibly the eggs of S. mansoni 

 were normal eggs similar to the abnormal forms, with 

 distorted spine, produced by 8. haematobium [271]. 



^ Obviously the possibility that, in Egypt, man harboured 



p ' ' ', two distinct species of bilharzia worm complicated the 



■x^.^rrr^.r transmlsslon problem, already rendered intricate by the 



INQUIRY. PI- . . „ . 



presence there of bovme and avian infections. 

 It was realized, however, that the full solution was not an essential 

 preliminary to the conduct of experiments which were more urgently 

 needed to provide the necessary data on which to base prophylactic 

 measures for the protection of the troops. The Bilharzia cercaricB iound 

 in Bullinus and in Planorhis, as well as other cercarioe, were found to react 

 in a practically identical manner to changes in their environment; whether 

 these were physical, such as exposure to heat, drying, etc., or chemical, 

 such as exposure to dilute amounts of sodium bisulphate, etc. The 

 B. cercari(B showed the same limited capacity to survive in water and 



