67 255 



A. Ebbeshornii Hudson. A. Girodi de Guerne. 



- Brirjhlwelli Gosse. - Imhofi dc Guerne. 



- priodonta Gosse. - Krumcri de Guerne. 



- Sieboldi Leydig. - bowesii Gosse. 



- intermedia Hudson. - ceijlonica Dadaj'. 



- triophthalma Daday. - cincinnatiensis Turner. 



- amphora Hudson. hiingarica Daday. 



- heluetica Imhof. - syringoides Plate. 



- Herrickii de Guerne. - Silvestrii. 



Harring (1913, p. 15) has reduced the number to only 6. 



A. Brightwelli Gosse. A. priodonta Gosse. 



- Herrickii de Guerne. - Sieboldii Leydig. 



- intermedia Hudson. - Siluestrii Daday. 



The species have been founded upon the structure of the jaws, number of e\'es, 

 form of ovarium, form of the body, form of the gastric glands, number of vibralile 

 tags, and shell structure of resting egg. In his admirable studies on A. amphora. 

 Powers (1912, p. 441) has made it probable that the difference in numbers of vi- 

 bratile tags are correlated with the general differences in the size of the organisms; 

 further that in the same species (A. Brightwelli) we may find trophi with and with- 

 out innertooth, and finally that the body-form in the same species undergoes the 

 greatest variation. This is to be understood in this way that no single animal goes 

 through all the various shapes; they are born with the shape they possess, and do 

 not change it in their life time; but their progeny may have a shape, different from 

 that of the parent. 



It will be understood that nowada3's it is a harzardous matter to found species 

 upon the three characters: number of vibratile tags, the jaws, and the outer form 

 of the body. As far as I can see, there is onh' a single good character, the shape 

 of the ovarium, by means of which the genus may be divided into two groups, those 

 with a round ovarium, and those with a horseshoe-shaped one. The main form for 

 the first group is A. priodonta for the other A. Brightwelli; to the first group may 

 further be referred A. Herricki de Guerne characterised bj' a peculiar glandular organ, 

 near the urogenital opening. It has been well described by Wierzejski. 



Most probably all As/3/a;ic/!/!«-species with a horseshoe-shaped ovarium are 

 subject to a greater or less polymorphism. To this group have been referred six 

 species. A. Brightwelli, A. aniphora, A. Sieboldii, A. Siluestri, A. intermedia and .4. Ebbe- 

 sbornii. Of these species .4. Silvestri characterised by the double humped form of the 

 female, well-described by Rousselet, has hitherto only been found in America and 

 in brackish water; it seems to be a rather distinct species. .4. Sieboldi Leyd. and .4. 

 Ebbesborni Hudson are unquestionably synonyms. According to the descriptions it 

 seems impossible to separate A. intermedia from A. amphora and provisionally .4. 

 intermedia may be regarded as a synonym for A. amphora. If this is correct, we 



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