151 



It appears that in the past undue stress may have been placed on 

 the importance of the ventral glands as a specific character in the genus 

 Linnbricilhts and also in Marionina. Southern ('09, p. 149) has 

 found great variation in them. "In some cases individuals have shown 

 well-developed glands, whilst in others from the same locality they 

 were either small, absent, or in different segments." Ditlevsen ('04, 

 p. 433) also throws doubt on the value of this character in the separa- 

 tion of species. No evidence of variation has been observed in the 

 ventral glands of L. rutilus. In every specimen of the long series ex- 

 amined they occur uniformly in XIII and XIV and in all cases showed 

 practically the same degree of development. The only \'ariable feature 

 is that the greatest development in these asymmetrical glands occurs 

 on the right side in some specimens and on the left side in others. 



FRIDERICIA Michaelsen 



Fridcy'icia is a well-defined genus, separated from the other genera 

 by the following important characters : the presence of dorsal pores, 

 and the size and arrangement of the setae. The setae are produced in 

 pairs in each bundle, the setae of the outer pair being the largest, the 

 next smaller pair being immediately within the largest, and these in 

 turn inclosing still smaller ones in the same manner. The group thus 

 formed is fan-shaped, with a pair of large outer setae and gradating 

 pairs between. Sometimes setas fall out, thus destroying the symmetry 

 of the bundle. 



Michaelsen ('00, p. 94) defines the genus as follows: "Borsten in 

 4 Bundeln, gerade, zu 2 im Biindel und dann gleich lang oder zu 

 mehreren und dann die inneren des Biindels mehr oder weniger regel- 

 miissig paarweise und stufenweise kleiner als die ausseren. Riicken- 

 poren mit Verschlusszellen meist vom 7., selten vom 6. Segm. an ^'or- 

 handen; Ivopfpoms meist klein, dorsal zwischen Kopflappen und i. 

 Segm. Lymphkorper von zweierlei Gestalt. Peptonephridien stets vor- 

 handen. Der Oesophagus geht allmahlich in den Mitteldarm fiber. Das 

 Ruckengefass entspringt meist postclitellial ; Blut farblos. Nephridien 

 meist mit grossem Anteseptale, in dem der Flimmerkanal schon Win- 

 dungen beschreibt. Samenleiter lang. Samentaschen meist mit dem 

 Darm kommunizierend, einfach oder mit Divertikeln." 



Fridericia is the largest genus of the family Bnchytraidce. In 

 1900, Michaelsen recognized twenty-one species, and since that time 

 the number has increased considerably, so that at present there are 

 about ninety sf>ecies referred to this genus. It appears that at least 

 three of these species are doubtful. Sixteen species have been described 



