AN ATTEMPT TO CLASSIFY EAETHWOEMS. 217 



A more usual variety of diverticulum of the canal is that 

 found in Lumbricus, and known as " calciferous glands," 

 or "glandes de Morren/^ Here there are three apparent 

 pouches on each side of the oesophagus^ two pairs lying in 

 Somite xi, and one pair in Somite xii. But of these, only the 

 first pair actually communicates with the gut ; the other two 

 pairs are not pouches, but thickenings of the oesophageal wall, 

 which is here hollowed out by a number of horizontal, antero- 

 posteriorly directed cavities, which end blindly behind, and 

 open into the first " pouch " in front. The horizontal lamellae 

 separating the chambers from one another contain blood- 

 sinuses, and are lined by large cells which secrete CaCOg ; this 

 escapes from the cells, or more probably the cells themselves 

 break away, and find their way by means of the anterior pouch 

 into the oesophagus. 



We have little or no detail as to the '' calciferous glands " 

 in other worms ; in some cases we do not even know whether 

 they produce lime ; but throughout I speak of them as "calci- 

 ferous glands." They are very frequently absent, and when 

 present are very variable in number and position. 



In some cases " salivary glands " are said to be found 

 amongst the muscles of the pharyngeal wall. 



II. Outlines of the Classification. 



The class Oligoch^ta may be divided into two sub-classes, 

 according to the presence or absence of asexual repro- 

 duction. 



Sub-class I. Naidomorpha. 



Order 1. Naidina. 

 Families 1. Aphanoneura. 



2. Naididse. 



3. Chsetogastridse. 

 [And the genus Ctenodrilus.] 



Small worms of relatively few somites ; blood uncoloured; male 

 genital pores in front of Somite vn, or in this somite. 



Asexual as well as sexual reproduction occurs. The 



VOL. XXXI, PART II. NEW SER. P 



