The Sheep-Fluke. 



9 



Australia, or is very rare. We are thus driven to the conclusion, now 

 accepted by all scientists in Australia, I believe, that wheat-rust with us 

 habitually omits one or more of its common European stages. 



It will be no matter for wonder to the reader that after having established 

 the above fact I should be prepared to discover a similar fact in the case of 

 the sheep-fluke, an organisation whose life 

 history is analagous in its complications. 



For a long time this suspicion seemed to be 

 supported by my investigations. Australian 

 snails were searched in vain for intermediate 

 forms of the fluke. No observer had ever seen 

 such a thing. Time passed, and still no inter- 

 mediate form could be found. At last, however, 

 about four years ago, snails containing the in- 

 termediate form of some species of fluke, pre- 

 sumably sheep-fluke, were found, and upon 

 careful examination and measurement were 

 found to be indeed the long searched for inter- 

 mediate form. Accordingly, after thorough 

 study and comparison at intervals lasting 

 through nearly two years, the formal announce- 

 ment of the discovery was made. The Austra- 

 lian snail harbouring the sheep-fluke turned out 

 to be a different species from the European snail 

 performing the corresponding function. Submitted to competent authorities 

 it was pronounced to be the species Bulinus Brazieri, a common and well- 

 known snail whose likeness is herewith presented. 



Fig' 7. — A snail that acts as inter- 

 mediate host of the sheep-fluke 

 in Australia. These are figured 

 from the specimens in which 

 the Australian intermediate 

 stage of the sheep-fluke >vas 

 first discovered at Austermere, 

 Moss Vale, 1893. Mr. Hedley, 

 of the Australian Museum, de- 

 termined the species of snail to 

 be Bulinus Brazieri. 



Fig. 8.— Sjiecimens of the cercaria or tad-pole-like intermediate form of the sheep-fluke found in the 

 snails shown in Fig. 7. These are shown in various natural attitudes, as seen with the micro- 

 scope. The mouth is well forward, and niay be seen in the upper left-hand figures. The 

 large circular ventral sucker is also swn best in the left-hand illustrations. Tlie power to 

 l)r()trude the sucker is indicated in the upper profiles. The drawings are faithful reproductions 

 of the author's original i)hotographs taken in 1893. 



Tliis snail may be found, sometimes very plentifully, on the stems of 

 plants growing in fresh water, as well as on other objects above or below the 

 surface of the water. They are essentially fresh water or rather amphibious 

 snails, never being found in an active condition very far from their aquatic 

 home. 



B 



