OLIGOCHAETA. 505 



In the Limicolae the atrium, which is a dilatation on the vas 

 deferens close to its opening, seems to correspond to the spermiducal 

 gland. 



In the Limicolae there is usually one pair of ovaries ^(except 

 Phreoryctes) and one pair of testes (except Lumbriculidae), and 

 their position varies somewhat in the different families. They are 

 placed further forward than in the Terricolae (for position see account 

 of families), and their ducts are short, opening on the segment 

 following that containing the gland. The nephridia of the segments 

 of the ovaries and testes disappear as soon as these organs begin 

 to develop. 



The ova of the Limicolae are much larger, and have more yolk 

 than the ova of the Terricolae. 



According to Beddard a trace of a second pair of ovaries can be made out in 

 the young of some earthworms (Lumbricus and Octochaetus) in the 12th segment. 

 In this case the number of ovaries will equal the number of testes, and the 

 series of gonads becomes a continuous one. 



The spermatozoa, which are filiform, develop in the sperm sacs, 

 into which the cells of the testis (progametes) are dehisced. When 

 ripe they are drawn into the vasa deferentia by the cilia of the sperm 

 rosettes, and passed down these tubes, which their presence renders 

 of an opaque white colour and so visible to the naked eye in 

 earthworms, to the exterior. Here they are taken up, in the manner 

 described below, by the spermathecae (receptacula seminis) of 

 another worm, where they are stored until they are required for use. 

 The sperm athecae are small vascular sacs, which open externally 

 near one end of the segment which contains them (usually the 

 anterior); the number of them varies considerably. In the Tei~ricolae 

 there are usually several pairs (4 or 5). Generally there is only one 

 pair in a segment. In the Limicolae they are generally contained in 

 the testicular segment. In Enchytraeus, and possibly other genera, 

 the spermathecae open into the gut as well as to the exterior. 



The capsulogenous glands, or as they are now called from their 

 supposed function, the albumen glands, are glandular developments 

 in the ventral body-wall in the generative segments of some earth- 

 worms. They probably secrete the albuminous matter found in 

 the cocoon. 



Spermatoplwres have been observed in some forms, both aquatic 

 and terrestrial (e.g. Tubifex, some Lumbricidae). They have a 

 somewhat elongated shape, and often have a certain complexity of 

 structure. They consist essentially of spermatozoa cemented together 



