THE ANATOMY. S P E R M ATO P H O R E S 135 



with the lumen of the spermathocal sac except indirectly. This communication is 

 brought about by the oviduct, the funnel of which is drawn out into two tubes, 

 one opening into the egg-sac, the other into the spermathecal one. In transverse 

 sections the anterior wall of the spermathecal one is seen to be formed by the 

 septum dividing segments xiii/xiv. The microscopic structure of the sac is as 

 follows : it is a thickish muscular coat, the fibres of which run in various directions ; 

 imbedded in this muscular coat is a structureless sheet, which has sharp edges 

 and is highly refractive ; it is undoubtedly a membrane, and is probably elastic 

 in nature, allowing for the distension of the sac with sperm, and its subsequent 

 shrinkage when the sperm is evacuated. The sac is lined with cells of an irregular, 

 somewhat elongated form, occasionally forming several pores ; these cells contain 

 numerous granules and are very similar to peritoneal cells in other parts of 

 the body. 



I have been able to trace the development of this sac through several stages. 

 In the youngest stage I found a sac below the nerve-cord freely opening into the 

 body-cavity ; the walls of this sac were formed by the intersegmental septum xiii/xiv 

 in front, and behind by a sheet of membrane, which traced backwards was seen to 

 connect that septum with septum xiv/xv. The pouch was formed by the attachment 

 of this membrane to the body-wall as well as to the septa, and was, therefore, freely 

 open at both sides. The ovary was attached to this membrane, just where it joined 

 septum xiii/xiv. In a later stage there was a more completely closed sac lying 

 beneath the nerve-cord, extending for a short distance into the thickness of the 

 body-wall ; above this sac, divided to embrace the nerve-cord and dorsally to the 

 nerve-cord, opened freely into the body-cavity ; here its walls were obviously formed 

 in front by septum xiii/xiv, and behind by the other membrane already referred to. 

 The ovary lay between the two membranes. On the ventral surface of the body, 

 just below the pouch, the epidermis had no gland-cells ; whether it is ultimately 

 invaginated to form the orifice of the spermathecal sac, or whether the sac bores its 

 way to the exterior I am unable to say ; but in any case the cavity of the sac 

 evidently begins as a coelomic space. 



ii. Spermatophores. 



A considerable number of Oligochaeta form cases for the enclosure of packets of 

 spermatozoa, which have been usually termed spermatophores. These were first 

 discovered in the Lumbricidae, and from their being attached to the exterior of the 

 body in the neighbourhood of the clitellum were regarded at one time as penes. 

 Spermatophores. although met with in a good many Oligochaeta. are apparently by 



