160 MERISTIC VARIATION. [part i. 



probably we shall be right in regarding the majority of these 

 variations as Homceotic. 



Lumbricus. Throughout this genus there is normally a 

 single pair of ovaries, placed in the 13th segment, on the posterior 

 surface of the septum between the 12th and 13th segments. The 

 following cases of supernumerary ovaries are recorded : 



97. Lumbricus turgldus : specimen having an extra pair of ovaries 

 in the 14th 1 segment. 



98. Specimen having an extra ovary on the right side in the 14th 

 segment. 



99. L. purpureus: specimen having an extra ovary on the left 

 side in the 14th segment. 



In all these cases the extra ovaries were in size, form and 

 position like the normal ovaries. There was no extra oviduct or 

 receptaculum ovorum, but the normal ovaries and oviducts were 

 present as usual. Bergh, R. S., Zeit. f wiss. ZooL, XLiv. 1886, 

 p. 308, note. 



100. Allolobophora sp. [partly = Lumbricus, the common Earth- 

 worm] : specimen having, in all, seven pairs of ovaries ; viz. a pair 

 in the 12th, 13th, 14th, 15th, 16th, 17th and 18th segments. Of 

 these all except the pair of the 13th segment are supernumerary. 

 Each of these ovaries was placed on the posterior face of a septum 

 in the usual position. The three anterior pairs in shape, structure 

 and position closely resembled the normal structures. Of these 

 the most anterior were slightly the largest. The four posterior 

 pairs were smaller and resembled the ovaries of a very young or 

 immature worm, but on examination all were found to contain 

 ova. The normal pair of oviducts were present and no extra ovi- 

 ducts could be found, though carefully sought for. Woodward, 

 M. F., P. Z. S. } 1892, p. 184, Plate xiil 



•101. Lumbricus herculeus, Savigny (= L. agricola, HofTmeister), 

 having an asymmetrical arrangement of the generative organs, &c. 

 On the left side the arrangement was normal ; the ovary being in 

 the 13th segment, the oviducal opening in the 14th, and the open- 

 ing of the vas deferens in the 15th segment (Fig. 24). 



On the right side each of these structures was placed in the 

 segment anterior to that in which it is normally found : the right 

 ovary was in the 12th, the external opening of the right oviduct 

 was in the 13th, and the external opening of the right vas deferens 

 was in the 14th segment. The spermathecse were normal on the 

 left side, being placed in the 9th and 10th segments, but on the 

 right side one spermatheca only was present, that of the 9th 

 segment. The vesiculse seminales were present as usual in the 

 9th and 11th segments, but there was no vesicula in the 12th 



1 In Bergh's enumeration the ordinal number of these segments is one less than 

 in that commonly used : the latter system is adopted above. 



