156 Phylum Plat helmint he s 



E. maculata does not feed very well on beef liver and is less easy to 

 maintain in laboratory culture than the preceding species. It is neces- 

 sary with this species to grind the liver in a meat grinder and wash it 

 thoroughly in running water. Small bits of such washed liver will usually 

 be accepted as food. This species, however, in general prefers pieces 

 of invertebrate flesh or liver or other flesh of tadpoles, fish, etc. 



Procotyla fluviatilis is the most difficult of our common species to keep 

 under laboratory conditions as it will eat nothing but live prey, such as 

 daphnids, amphipods, and isopods. It will sometimes accept blood clots, 

 but in general it is impractical for laboratory purposes. 



Sexual material. Zoologists at times desire sexually mature material 

 for class or experimental purposes. In general those species which re- 

 produce extensively by asexual methods are seldom found in the sexual 

 state; this statement applies to E. dor otocephaly, E. agilis, and Fonticola 

 velata. E. maculata and its various varieties are commonly sexual 

 throughout the U. S. in the summer time and numerous egg capsules will 

 be found on the under side of the stones in the habitat of this species. 

 It is a curious fact, however, that E. maculata is apparently never sexual 

 in some localities or regions while always sexual in the summer in others. 

 Sexual specimens will continue to lay eggs under laboratory conditions. 



Species which do not reproduce asexually are commonly in the sexual 

 state at some definite season of the year. For Procotyla fluviatilis, which, 

 owing to its transparency, is our most suitable species for preparing slides 

 showing the reproductive system, the time of sexual maturity extends 

 from September into the winter or even, in some localities, into spring. 

 Fonticola morgani (=Planaria truncata) is sexual in summer, as is also 

 Polycelis coronata of mountain streams of the northwestern U. S. 



The only species which may be depended upon to lay egg capsules 

 regularly under laboratory conditions is Curtisia foremanii (=Planaria 

 simplissima) . This species occurs throughout the Atlantic coast states, 

 may easily be cultivated in the laboratory on beef liver, and will lay egg 

 capsules continuously for a long period. The young soon grow up to 

 sexual maturity and also lay in their turn so that a continuous supply of 

 capsules is assured with this species. 



Class Trematoda 



THE PARASITIC FLATWORMS 



H. W. Stunkard, University College, New York University 



REPORTS on culture methods for different species of parasitic flat- 

 ^ worms, similar to those described for free-living invertebrates, can 

 not be made, because at the present time there is no known culture 



