614 W. S. NICKERSON, 



family Äspidohothridae will liave to be recogDized as a distinct geiius. 

 Furthermore every species of which a cousiderable number of spe- 

 ciraens has beeii carefully investigated has been found to exhibit 

 Variation in this respect. Stafford ('96) says of Äspidogasler conchi- 

 cola: "The number of fossettes [= alveoli] varies with the number of 

 transverse ridges which latter increase with the age of the animal. 

 .... The greatest number of acetabula that I have counted in the 

 adult is 118." Jägerskiöld ('99, p. 202) says concerning Macraspis 

 elegans: "Auf diesem Stadium .... ist die Zahl der Saugnäpfe des 

 Ikuchschildes ziemlich gering — nur ca. 10. Nach hinten geht aber 

 das Bauchschild ohne scharfe Grenze in ein an Kernen sehr reiches 

 aber ganz muskelarmes Blastem über, das bis zum Hinterrande des 

 Körpers verfolgt werden kann. Es entstehen offenbar aus diesem 

 Blastem die neuen Sauggruben. Diese nehmen somit von vorn nach 

 hinten an Zahl zu. Eine sehr ähnliche Bildungsweise wird .... für 

 Stichocotyle nephropis beschrieben. An dem grössteu und ältesten 

 meiner Exemplare habe ich beinahe 100 Sauggruben zählen können, 

 und doch folgt auf die letzte derselben noch ein kleines Blastem, wie 

 das oben besprochene." Odhner ('98, p. 512) writes of Stichocoüße 

 nephropis: "Auf der Bauchseite findet sich eine einfache Längsreihe 

 von Saugnäpfen, deren Zahl je nach der Länge des Wurmes, zwischen 

 20 und 27 wechselt." In Cotylogaster occidentalis I have found the 

 Variation in the number of alveoli in the seven specimens examined 

 to exceed the difference said to exist between Cotylaspis insignis and 

 C. lenoiri. Furthermore I learu from Prof. Osborn that he has found 

 the alveoli in the diflerent specimens of Cotylaspis insignis to show 

 a certain amount of Variation in number and arrangement. We know 

 that in several Aspidobothrids {Aspidogaster , Macraspis, Sücliocotyle) 

 the number of alveoli increases with the age of the animal. We have 

 however no means of knowing that Poirier's specimens were fuUy 

 adult and that they had attained the maximum number. The dif- 

 ferences in the five cases cited are unquestionably only individual 

 differeuces. I certainly am unvvilling to recognize a similar difference 

 between Cotylaspis insignis and C. lenoiri as of generic importance 

 and should cousider it unwise in any case to select as the basis of 

 generic distinction so variable a character as the number of alveoli 

 in the ventral sucker has been shown to be. 



The third point of difference which Kopoid mentions — in habit 

 — I regard as soraewhat less than the use of the terms ecto- and 

 endoparasitic immediately suggest; for though the inferior of the 



