TREMATODA 



45 



another minute two more emerged. In twenty-six minutes the 

 fourth, in twenty-eight the fifth, in thirty-two the sixth, in 

 thirty-four the seventh, in thirty- seven the eighth, in thirty-eight 

 the ninth, in forty the tenth, in forty-three the eleventh, and 

 in forty-six minutes the twelfth, respectively made their 

 appearance." 



Now, this rapid mode of birth and emergence from the shell 

 is very much more striking in the case of eggs which are placed 

 in perfectly pure water ; for, whilst the eggs are still in the 

 urine, there appears to be neither the power nor the inclination 

 on the part of the embryo to escape ; but, on isolating and 

 placing them in suitable conditions, their behaviour is even more 

 remarkable. In a space of less than two minutes I have 

 repeatedly seen the hitherto motionless embryo alter its shape 

 by contractions, become violently agitated, anji burst out of its 

 shell in the condition of a free- 

 swimming animalcule. More- 

 over, it is worthy of remark 

 that the eggs and larvae of Bil- 

 harzia soon perish in stale urine. 

 " On the 16th of August, 1870, 

 I placed about a thousand eggs 

 in a quart of fountain- water, to 

 which only a drachm or rather 

 less of urine had been added. 

 At the expiration of forty- eight 

 hours not a single living em- 

 bryo could be found. I subse- 

 quently ascertained that I could 

 not keep the embryos alive for 

 twenty-four hours in any water 

 in which I had introduced the 

 smallest trace of mucus, blood- 

 corpuscles, urinary crystals, or 

 decomposing matters of any kind. 

 All sorts of reagents speedily 

 killed the larvae. Mere discolora- 

 tion by carmine solution, or by 

 the addition of a drop of the solu- FlG 

 tion of permanganate of potash, 

 instantly caused them to assume grotesque and unnatural shapes 

 (figs, 13 and 14), death sooner or later following as a result 



