ENCHYTR^ID^ fJ2 



than in that species. Two large sperm-sacs extending through several 

 somites anterior to XI. In shape these sacs resemble those of £^. 

 sax I cola. 



Genus Michaelsena Ude (part). 



Definition. — SetaB straight, more or less absent in majority of the 

 somites. Head-pore between prostomium and somite I. No dorsal 

 pores. Esophagus gradually merging into the intestine. Dorsal ves- 

 sel rises posterior to clitellum, and is without cardiac gland. No pep- 

 tonephridia. Testes solid. Nephridia as in Enchytrceus . Penial 

 papillas without interior muscular strands. No penial bulbs. 



To the definition given originally by Ude I have added the charac- 

 teristics of the penial bulb, and modified that referring to the setae. It 

 is to my mind evident that if we are to recognize the genus Michael- 

 sena we must make the definition wide enough to include both Mich- 

 aelsen's species, EncJiytrcsus monochcetiis^ and my new species, 

 Michaelsena paucispina. These species differ but slightly from M. 

 subtilis Ude, the differences referring only to the number of missing 

 setae. In M. paucispina the setae are entirely absent on the anterioi' 

 three somites, and in all the other anterior somites only two ventral 

 setse are found in each somite. In some of the posterior somites there 

 are four setae in each somite. In Enchytra:us niotiochcetus a further 

 reduction has taken place, as there are no setae in the anterior five so- 

 mites. Then follow other somites with only ventral setae, while the 

 majority of somites seem to possess four rows of single setae. In M. 

 subtilis another step in the reduction has been taken, and we find in 

 this species only ventral setae In somite IV, V and VI. In all the other 

 somites the setae are absent. I cannot see how we could very well in- 

 clude one of the above species in the genus and exclude the others. 

 So far as known there are no characteristics of suflScIent Importance to 

 separate these three species In different genera. 



SYNOPSIS OF SPECIES. 



1. Michaelsena subtilis Ude. Setse found only in somites IV, V and VT, and 



here only two pairs corresponding to the ventral fascicles. Size 5 to 6 mm. 



2. M. monochcpta (Michaelsen). The anterior four or five somites without any 



setae. The following few somites possess only single ventral setae, while 

 all the other somites possess four single seta, each setse corresponding to 

 single fascicle. Length 7 mm., width .25 mm. 



3. M. paucispitia sp. nov. Somites I, II and III without setae. All other 



anterior somites with two ventral setae, each seta corresponding to a fasci- 

 cle. The posterior somites with four setse each, each seta corresponding to 

 a fascicle. Length 7 mm., width .2 mm. 



It may be noted that all the three species seem to be marine forms, 

 occurring along the seashore among seaweeds. 



