W. BALDWIN SPENCER. 



immediately above the point of union of (1) the tubes coming 

 from the spermatheca on either side^ and (2) the vagina 

 (= uterus of the adult) entering from the ventral surface. 



The walls of the oviducts near to the ovary are much more 

 cellular in appearance than lower down. As the duct on each 

 side passes through the hook-gland it is accompanied by a 

 certain number of strongly marked muscle-fibres^ which run 

 parallel to its course, but are independent of its walls. The 

 latter are formed of a layer of cells internally, which become 

 somewhat indistinct as the oviduct becomes swollen out with 

 eggs, and external to this a layer of muscle- fibres crossing one 

 another obliquely, and with a general trend in the direction of 

 the length of the oviduct. These fibres lie in an external coat 

 of connective tissue, in which at earlier stages no muscle ele- 

 ments could be determined. 



The structure of the walls forming the swollen common 

 portion is the same ; whilst immediately in front of this the 

 lumen of the tube narrows^ the cells of the internal layer 

 become elongate and thrown into ridges, and, in addition to 

 the fibres mentioned above and internal to them, there is 

 developed a special series of circularly disposed muscle- 

 fibres. The longitudinal fibres are strongly developed, and 

 run backwards in the mid-dorsal and ventral lines, to be con- 

 tinuous with those on the surface of the vagina (= uterus) 

 (figs. 40, 54, M. 8). 



The portion of the duct provided with this special muscular 

 apparatus is equivalent to that described by Leuckart, which 

 he is without doubt right in regarding as a special struc- 

 ture for the purpose of forcing the ova through from the 

 oviducts into the vagina. The swollen portion with thin walls 

 which lies immediately in front of this, and is directly con- 

 tinuous with the two oviducts^ appears not to be represented in 

 his species. In P. teretiusculum the oviducts open widely 

 into it, and consequently it is filled with ova. Figs. 40 and 41 

 represent somewhat diagrammatically the relationship of these 

 parts of the reproductive organs. 



(c) Spermathecae and Spermathecal Ducts. — The 



