327 



NOTE ON THE DUCT OF THE SPERMATHECA OF HYALINIA 



EXCAVATA. 



By A. E. Boycott. 



Bead 11th June, 1915. 



PLATE X. 



The curious anatomy of the duct of the spermatheca ia JIi/. excavata 

 and nitida was noticed by C. Ashford, and first, I think, described by 

 "VV. Moss.^ They found that passing downwards from the spermatheca 

 the duct bifurcated, one brancii opening into the vagina in the 

 usual way, while the other came into relation with the penis and 

 possibly opened into it. P. Pelseneer' found that this second branch 

 did not actually form a passage into the lumen of the penis, but 

 ended in a blind sac surrounding the lower end of the penis and 

 dart-sac.^ 



So anomalous an arrangement seemed worth reinvestigation, and 

 I have examined in detail, by means of complete series of microscopical 

 sections, five specimens out of a number collected at Portmadoc 

 (Carnarvonshire) in August, 1913. As appears to be usual at that 

 time of year, few of them had darts ; of the specimens examined two 

 possessed spicula, and in the other three the dart-sac was empty. 



The accompanying sketches of nine sections, approximately 

 transverse to the general axis of the genital apparatus, show the 

 condition found. The sections were each 0*009 mm. thick, and the 

 numbers attached to each show its position in relation to the section 

 containing the external genital orifice, which would be numbered 0. 

 Section 133 shows the oviduct with the vas deferens and spermatheca 

 duct. In section 129 the latter has divided into three branches, one 

 of which (duct A) almost immediately opens into the oviduct, the 

 transition being shown in section 1 24. The other two (ducts B and C) 

 run for a short distance in close connexion with the wall of the 

 oviduct, but presently separate from it, and from one another, as seen 

 in section 107, which shows also the passage of the vas deferens into 

 the penis, and the upper end of the dart-sac. Section 97 shows penis, 

 dart-sac, free oviduct, duct B close to the dart-sac, duct C in contact 

 with the oviduct, and also the upper extremities of the sac (S) into 

 which duct B opens. This opening is placed just below section 94. 

 In section 90, penis, dart-sac and oviduct are confluent, duct B has 

 disappeared into the sac which is about here at its largest, and duct C 

 is still separate. The opening of duct C into the vagina concurrently 

 with the junction of the penis and dart-sac is shown in section 85, 

 while section 77 shows the common genital passage and the lower 

 extremity of the sac. 



^ Journal of Conchology, vol. viii, pp. 421, 1897. 

 ^ Mem. Acad. roy. Belgique, vol. liv, p. 62 (of reprint), 1901. 

 ^ See the description and figures of J. W. Taylor, Monograph, vol. iii, 

 pp. 135, 142. 



VOL. XI. — .\UGUST, 191-5. 24 



