
578 RECORDS OF THE S.A. MUSEUM 
spaced out, in the tail-stem (fig. 14). The flame-cell formula is thus 
2((2+ 2) + (14+2-+ (2))]=18. The posterior tubule is also furnished with 
two patches of cilia, just after its origin from the main duct. From the posterior 
border of the bladder the central exeretory canal of the tail arises; it forms an 
island of Cort at the junction of body and tail-stem, and then passes down the 
tail-stem to divide at the origin of the fureae into two ducts. The opening of 
these, as far as could be determined from preserved material, probably oceurs half- 
way along the furcae (fig, 14). 
Sporocyst. 
The single host snail of this parasite lived in the laboratory for nearly three 
months. Upon death it was dissected; most of the liver had been replaced by 
masses of tangled, whitish sporocysts. he first attempt to disengage one of these 
liberated an immense number of actively moving diplostomula, and every sporoeyst 
was packed with them (fig, 15), but no cercariae were seen, althongh the latter were 
being emitted only twelve days earlier. The sporoeyst itself consisted of nothing 
more than a delicate tubular skin around the diplostomula. A long sporoeyst 
measured 5 mm.; but most of them were shorter. 
Precovious development of diplostomula within the parent sporoeyst has 
been recorded for various species, including C. meladena Johnston and Angel 
(1942), observed in this laboratory. In the report on this observation, an account 
was given of other observations of this phenomennon, which is apparently confined 
to the Diplostomes, and also a discussion of the possible causes of such pre- 
eocious development. 
METACERCARIA, 
The fish, Gambusia affinis, resists experimental infection with Cercaria 
ameriannae. Tadpoles of Limnodynastes sp., probably L, dorsalis, are however 
highly susceptible to infection. Two of these were placed in contact with large 
numbers of ceveariae. On the following day both tadpoles were dead, and micro- 
seopical examination showed numerous tail-less cereariae moving through the 
tissues. Lighter infections employed subsequently enabled diplostomula of eon- 
siderable size to be raised, They do not secrete a eyst wall, and for some time 
after penetration are to be found wandering in the tissues. Eventually they 
penetrate the notochord, and develop within it in numbers. Sections show that, 
where they penetrate, the notochord becomes hollowed out. Usnally a group of 
about half-a-dozen are found together. 
The diplostomula are very active when alive, and are very extensihle—there 
may bea difference of 824 between the length when extended and the length when 
