430 DR W. CARMICHAEL M'lNTOSH ON THE STRUCTURE OF THE 



Fig. 10. Transverse section through the contracted reservoir-region of 0. alba, showing the complex 

 spiral arrangement of the fibres. x 55 diameters. 



... 11. Superficial structure of the reservoir- and stylet-regions in the same species. 



... 12. Central stylet and basal apparatus with radiating fibres in Tetrastemma vermiculus. x 350 

 diameters. 



... 13. Stylet-region of a young 0. alba, some weeks older than that represented in fig. 2. 

 x 350 diameters. 



... 14. Transverse section through the posterior chamber of the proboscis in a large example of 

 0. alba. The circular and longitudinal muscular and the mucous coats are well shown, 

 x 90 diameters. 



... 15. Young Tetrastemma variegatum, shortly after extrusion from the egg, and somewhat com- 

 pressed, so as to show its cellulo-granular structure. x 350 diameters. 



... 16. Portion of the long posterior chamber of the proboscis of O. purpurea, showing the charac- 

 teristic plaits of the mucous surface. x 90 diameters. 



Plate X. 



Fig. 1 . Enlarged view of the anterior end of B. olivacea as a transparent object. 



2. Transverse section through the curious example (probably a variety of Meckelia) from 



Balta ; d, external layer of cutis ; <7', basement-layer ; e, longitudinal muscular layer ; 

 ea, dorsal sub-divisions of the latter coat in the central line ; e , circular muscular coat ; 

 j, section of the oesophageal region of the digestive tract ; ja, distinct band of muscular 

 fibres enclosing the latter; n, lateral nerve ; o, sheath for proboscis; r, vascular spaces, 

 x 55 diameters. 



3. Transverse section through the body of Ccpha/atlirix filiformis. The proboscis is coiled in 



its sheath. x 90 diameters. 



4. Transverse section just behind the tip of the snout of Borlasia olivacea. The grouping of 



the pigment (3) readily enables the observer to distinguish the dorsal from the ventral 

 surface ; 2, powerful series of fibres arching over the channel leading to proboscis, and 

 which radiate into the surrounding stroma (/,-). x 55 diameters. 



5. Portions of the inner surface of the proboscis of the same species, showing the glandular 



papilla?, slightly compressed. x 700 diameters. 



6. Gland-cells from the wall of the digestive cavity of Ommatoplca alba. x 400 diameters. 



7. One of the same slightly compressed glands. x 700 diameters. 



8. Contents of the same gland-cells, with oil-globules. x 700 diameters. 



9. Spermatozoa of Borlasia olivacea. x 700 diameters. 



Plate XL 



Fig. 1. Transverse section through Borlasia olivacea, just at the commencement of the oesophageal 

 region ; 2, radiated or slightly arborescent arrangement of the external longitudinal 

 muscular coat at the sides of the mouth. The thick folds of the oesophagus are seen 

 almost at the termination of the anterior cul-de-sac. x 90 diameters. 



2. Arrangement of the ova in the ovisacs of Tetrastemma vermiculus ; a, proboscis ; o, probos- 



cidian sheath. Only a fragment of the body is represented. x 24 diameters. 



3. Spermatozoa of Ceplialotlvrix filiformis. x 900 diameters. 



4. Spermatozoa of Lineus longissimus. x 900 diameters. 



5. Spermatozoa of Borlasia octocnlata. x 800 diameters. 



6. Transverse section through the body- wall of Lineus longissimus at a somewhat narrow por- 



tion ; d, external cuticular layer ; d", pigmentary layer divided into two strata by a defi- 

 nite black band (2) ; 3, curious translucent stratum, cut into somewhat regular spaces. 

 Other letters as usual. x 210 diameters. 



7. Longitudinal section of the tissues of the body-wall in the same species ; 4, 4, sections of the 



transverse connecting trunks between the lateral and dorsal vessels ; 5, granular stroma 

 within the inner longitudinal muscular coat, supporting the former and various other 

 tissues. x 90 diameters. 



8. Transverse section of the body- wall of Borlasia olivacea. x 350 diameters. 



9. Proboscis of Cephalothrix filiformis, slightly everted, so as to exhibit the acicular papilla^. 



x 350 diameters. 



