412 J- Stafford, 



he thought had been seeii but not definitely recognized by botli 

 Pagenstecher and Looss. In a later work Loo^s perceived that 

 tlie forms described by Bensley were distinct American species and 

 named tliem Gorgodera amplicava and Gorgodera simplex. The earlier 

 publication by myself simply records the occurrence of this Distome. 

 In the present paper I shall attempt to show that there occur no 

 less than 5 species of Gorgodera in onr frogs and toads, Gladly 

 accepting the generic and specific nomenclature of Looss, and siip- 

 plying as well as I can designations for the other three species, 

 they may be arranged in order of size thns: 



In Order to facilitate comparison, the drawings are made as 

 nearly as possible to the same scale of magnification of an average 

 fuU-grown specimen in each case, They show the most easily de- 

 tected characters which are likewise the ones that are at greatest 

 variance in the different species and consequently best suited for 

 instituting distinctions, When one comes to the finer microscopie 

 anatomy one expects to find, in a group whose members are so 

 closely related as these, only few and slight differences ; consequently 

 descriptions of the Integumentary, Parenchymatous, Muscular, Glan- 

 dulär, Excretory and Nervous Systems are here neglected. The 

 Intestinal System of the x4_merican forms, although agreeing in its 

 parts (mouth, CBSophagus, cgeca) with the European species, may 

 yet have certain different relations to other organs, as e. g. in the 

 eseca being wide apart, near the sides of the body, or approximated 

 towards the centre. The most important sources of contrast are to 

 be sought in the External Features, the Reproductive Organs, and 

 the Hosts. The Cuticle and the Egg, sometimes so convenient and 

 so trustworthy in distinguishing species, are in this case either 

 useless or unsatisfactory. In all five species the cuticle is perfectly 

 smooth, without a trace of spines. Its thickness varies with 

 the region and the state of contraction of the part. The e^^ of 

 Gorgodera cygnoides, as observed by Schauinsland and Looss, in- 

 creases in size while passing through the long uterus. In these 



