FAlf.MKKs' INSTrn'TKS. SOU 



bn'jidtli, aiul then (lecreasos prn^'lii-il'y i" \vi<lili to the posterU*!' oiul wliicli 

 is bluntly i)()int«Ml: cuticle is covcrctl with nnuicious sjiincs jilaccd side 

 ii.v side in altcrnatinji' rows; oral sucker is anterior. ronn<l and lenninal, 

 but iuelines ventral; acetabulum about :>-4 nun. caudal of oial sucker, with 

 which it closely ajirces in size; yenitnl pore median, about half Avay l)e- 

 tween oral sueker and acetal)ulum: oesophauus rarely over 1-1-V. times as 

 long as the pharynx; intestine tlentritic: ciirns Cretiuently extended from 

 pore and then recurved; testicles profusely branched, situated in the 

 .!j;reater part posterior to transverse vitello-d-uct. Vulva is at side of cirrus; 

 uterus forms a rosette Avith its numerous coils, and is fre<iuently visil)le 

 to the naked eye as a dark brown spot, immediately posterior to the 

 acetabulum; ovary branched, anterior of tranverse vitello-duct; vitello.sjene 

 glands profusely branched, and occupy the entire margin of the body from 

 acetabidum to posterior extremity; they lie (h>rsally as well as ventrally 

 of the intestine, becoming wider posterially. Oviparous. 



p]ggs; oval. 0.13-0.14 mm. long by 0.075 to O.OU mm. broad; miracidium 



conical, ciliated with oval papillae, two cup shaped eye spots, rudimentary 



-intestine; metamorphosis (sporo cyst, redia, ceroariae) take place in small 



snails of the genius Liuneae; L., trucatula, and othersj. Cercaria wliitish, 



owing to excessive development of capsule glands; encysts upon ]»lants. 



late History of Fluke and Method of Infection.— Although the life 

 history of flukes is of^little importance to us at present, it is well for us to 

 know something about tlieir deveh)pment. Their life hist(n-y in l)rief is as 

 follows: Kach adult worm is capable of producing an immense nuni])er 

 of eggs (thirty-seven lo forty-five thousand). These pass doAvn the bil- 

 liary i)assages into tlie intestines and become mixed AA'ith tlie faeces. 

 Those that reach some favorable place for development afttr a lt)ng or 

 short period of incubation (from ten days to three montlis), depemling on 

 the amount of heat and moisture, become a ciliated embryo. The cili- 

 ated emi)ryo (.Miraciiliiuiu swims aromid in the water and seeks certain 

 snails (Linnea trucatula. L. rudeliaj, .and penetrates into the respiratory 

 cavity of these animals and encysts. The sporocyst Avhich it is now called, 

 at the end of aliout foiu-teen days is about one fiftieth of an inch in length 

 and the germ cells i)resent develop into a third generation. knoAvu as 

 rediae. Tlie rediai' escape from the sporocyst AA'lieu the latter is from tAVO 

 to four weeks old. They then wander to the li\'er of the snail and from 

 the germ cells preseni in tlie body cavity of the parasite dcA'elop the next 

 generation, tlie <ercariae. This latter form resembles the adult parasite. 

 It may remain in the body of the snail for some time or pass out and 

 attach itself on the grass (»r aijuatic plants around the margins of the 

 pond and encyst. Tlie ditfeiciit animals become infected from eating these 

 snails along with the food or from eating grass infested with the cer- 

 cariae. The development will last from ten to twelve Aveeks. Each sporo- 

 cyst may give rise to from five to eight rediae and each rediae to from 

 twelve to t\\<'iit\' cercariae. 



