Alien Oligochaets in England. By Rev. H. Friend. 149 



1895. rive years later Michaelsen (6') tabulated no fewer than 

 eleven, and two other species have since been added to the list. 

 The present form, therefore, brings the known species of Kerria 

 to fourteen. 



II, — Distribution. 



As already stated, the iirst species, Kerria halojjJiila Bedd., 

 which forms the type, was found in salt water in the Pilcomayo. 

 Later research has added many South American, West Indian, and 

 Californian localities to the list. Mention may be made of Buenos 

 Ayres, Uruguay, Southern Brazil, Paraguay, Valparaiso, Juan 

 Fernandez, and San Jose del Cabo. The species are not all found 

 in salt or brackish water, but flourish also in fresh water and in 

 soft ooze or mud, Michaelsen summarizes the matter thus : — 

 " Terrestrisch, im Siisswasser und in salzhaltigem Wasser. Sub- 

 tropisches Siid-Amerika und Nieder- Calif ornien." It is, therefore, 

 clear that when the genus is found represented in England it cannot 

 well be indigenous. 



o 



III. — Generic Characters. 



Though Beddard did not summarize the generic characters in 

 his original description, he supplied a definition in his Monograph, 

 which reads as follows :— 



" Setse paired, present on all the segments of the body except 

 seta 2 on segments xvii and xix of some species. No dorsal pores. 

 Nephridia paired. One pair of testes in x. Spermiducal glands 

 lined by a single layer of cells ; no penial setae. Spermathecse 

 with or without diverticula." 



The difficulty with this definition is that it leaves one in 

 doubt about the allied genera, as the author himself realized. 

 " Very little is wanted," he writes, " to convert the (type) species 

 into an Ocnerodrilus," while " it undoubtedly agrees in all those 

 points which are made use of to define the genus Acanthodrilus. . . 

 If it were not for the position of the calciferous (oesophageal) glands, 

 all the resemblances between this worm (the type of the genus 

 Kerria) and Ocnerodrilus might fairly be set down to a convergence 

 due simply to degeneration." 



The researches of Rosa made it possible to enlarge and define 

 the generic characters with greater exactitude, and Michaelsen {6) 

 was able in 1900 to give the following as the definition of Kerria : — 



" Mannliche Poren am 18 Segm. ; Prostataporen 2 Paar, am 

 17 und 19 Segm. ; Samentaschenporen meist 2 Paar, auf Inter- 

 segmtf. 7/8 und 8/9, selten die vorderen fehlend, 1 Muskelmagen 

 im 7 Segm. oder keiner ; 1 Paar seitliche CEsophageaitaschen im 



April 19th, 1916 m 



