630 OLIGOCHAETA 



Here it will be seen that there are no conclusions to be drawn ; that is to say, 

 no conclusions which bear upon the major divisions of the family; however, most 

 of the Old -World genera agree, while the New-World forms are divisible into 

 two sections, not perhaps altogether natural, since Pontoscolex is divorced from its 

 certainly near ally Diachaeta. 



In Trichochaeta barbadensis, and possibly also in T. hesperklum, there are two 

 sets of structures which may be compared to the ' Glands of Morren ' in Lumbricus; 

 in segments x, xi, xii the oesophagus is widened and its .walls are much folded and 

 vascular; in T. barbadensis I have found that this section of the oesophagus, which 

 is not sharply marked off from the rest, produces crystals precisely like those which 

 are excreted by the calciferous glands of other earthworms ; there seems, therefore, 

 to be very little doubt that this region of the oesophagus is, at any rate, the 

 equivalent, so far as function goes, of the calciferous glands ; but there is no formation 

 of caeca opening into the oesophagus ; we have simply a tract of oesophagus rather 

 different in structure from the rest of the oesophagus ; it requires, however, a very 

 little change to convert this tract of gut into a series of glands like those of 

 Pontoscolex for example. But the segments occupied by the calciferous glands of 

 Pontoscolex, and those in which the oesophagus of Trichochaeta has undergone the 

 modification just referred to are not the same ; in Pontoscolex the glands in question 

 lie in segments vii, viii, ix. We are fortunately relieved from the difficulty of 

 deciding this matter by the occurrence in Trichochaeta of three pairs of rudimentary 

 caeca in segments vii, viii, ix ; the minute structure of these will be described 

 (below) ; it is clear that they are the exact equivalents of the calciferous glands of 

 Pontoscolex. It is, therefore, at least probable that in the Geoscolicidae generally, 

 anteriorly situated calciferous glands are not the exact homologues of posteriorly 

 placed calciferous glands. We can arrange the genera into two series according 

 to the position of these glands, as will be seen from the table on p. 631. 



i. SUBFAMILY GKOSCOLICINAE. 



DEFINITION. Spermathecae one to four pairs placed in neighbourhood of gizzard. 



As already remarked, all the genera of this subfamily, with the exception of 

 Ilyogenia from Natal, are tropical American in habitat, ranging from the West Indies 

 even so far north as the Bermudas (Onychochaeta) to Brazil ; they do not appear to 

 occur in the more southern regions of that continent. 



