1904.] ON TWO SPECIMENS OF HYBItlD GROUSE. 411 



In conclusion, I have to acknowledge my indebtedness to Dr. 

 J. F. Gemmill for the privilege of working up my material in his 

 Laboratory at Glasgow University, To Dr. Teacher, of the 

 Hunterian Museum, also I owe and now tender my best thanks. 



Papers referred to. 



(i.) V. Graff. — ^^Die Organisjition der Turbellaria Acoela. 



1890. 

 (ii.) V. Graff. — Zoologischer Anzeiger, 1892. 

 (hi.) v. Graff. — Die Turbellarien als Parasiten und Wirte. 



1903. 

 (iv.) BoHMiG. — Die Turbellaria Accela der Plankton-Expedi- 

 tion. 1895. 

 (v.) Sabussow. — " Haplodiscits iissoivi, n. sp." Mitth. zool. 



Stat. Neapel. 1896. 

 (vi.) MoNTiCELLi. — " A proposito del Haplodiscus ttssowi." 



Atti Soc. Natur. Modena, (4) vol. 1. 

 (vii.) Sabussow. — '■'^ Bdhmigia maris-albi, g. et sp. n." Zool. 

 Anzeig. xxii. p. 89. 



EXPLANATION OF PLATE XXV. 



All the figures except fig. 1, which is diagrammatic, were drawn from 

 photomicrographs of sections. 



Ziist qf Reference Letters. 



Br. Brain, c. Cuticle, d.p. Dermal layer of the parenchyma, d.v. Digestive 

 vacuole. F.d. Frontal ducts. F.ff. Frontal glands. F.o. Orifices of frontal ducts. 

 m. Mouth, mus. Muscular layer, ot. Otocyst. ov. Ovary, p. Penis, p.a. Arma- 

 ture of penis, p.s. Parenchymatous strands, s. Cilia, t. Testis, vag. Adven- 

 titious "vagina." v.s. Vesicula seminalis. 



Fig. 1. The general topography of Avagina incola shown diagrammatically. X 20. 



2. Median longitudinal section. X 20. 



3. Integument and dermal parenchyma. A X 600. B X 700. 



4. Mesial longitudinal section showing " digestive vacuole." X 75. 



5. Longitudinal section of anterior end showing frontal glands. X 150. 



6. Longitudinal section through male apparatus. X 150. 



7. Longitudinal section of posterior extremity showing adventitious opening hy 



which ova are being extruded. X 45. 



3. On Two Specimens o£ " Riporre " with known Parentage. 

 By Dr. Einar Lonnberg, C.M.Z.S., &o. 



[Received February 6, 1904.1 



(Plate XXYI.) * 



When the author of these lines last summer visited the town 

 of Pitea, in JSTorthern Sweden, he had the oppoi-tunity of seeing 

 two fine specimens of Riporre, then in the possession of Dr. T. 

 H. Bjbrkbomf. The great interest connected with these two 

 specimens is that their parentage is fully known. They are from 



* For explanation of the Plate, see p. 415. 



t They are now in the zoological collections of the Gothenburg Museum. 



