W. JR. Coe — Anatomy of Cerehratulus lacteus. 509 



Figure 4. — Transverse section through the head in the region of the mouth; o, 

 mouth; &&, buccal vessel; vn, vagus nerve; Zc, lateral cord; dn^ dorsal nerve; 11^ 

 lateral lacuna ; ps, proboscis -sheath. Above the mouth is seen a thick band of 

 horizontal muscles (Am) connectiug the two sides of the incomplete circular mus- 

 cular layer (cm). The cutis (cw) in this region is very thick and the tubular 

 glands are much elongated ; x 8. 



Figure 5. — Transverse section of the lateral cord in the oesophagal region. A large 

 mass of ganglion-cells {gc) is seen below, and a similar mass above, the fibrous 

 core (/c); C5, inner sheath of connective tissue; cs\ outer sheath; c, loose con- 

 nective tissue; m, a few longitudinal muscular fibres; x 110. 



Figure 6. — Horizontal, longitudinal section through the ventral portion of the brain. 

 On the right-hand side, the proboscis-nerve (pn) is seen to leave the fibrous core 

 of the ventral commissure. The vagus nerve {vn) originates from the inner 

 border of the ventral brain-lobe; gc^ ganglion-cells; ml, median lacuna; x 40. 



Figure t. — Side view of brain and side-organ dissected from a small specimen pre- 

 served in a dilute solution of formalin; x 20. 



Figure 8. — Diagram of the brain and large nerves of the head. Partly reconstructed 

 from sections, and partly from a sketch of the organs in the living animal. The 

 extent of the cephalic slits {Is) is indicated by a dotted line. The proboscis-nerves 

 {pn) are seen to originate at the anterior border of the ventral commissure. 

 After running forward a short distance they bend inwards to enter the proboscis. 

 The dorsal brain-commissure {dc) is seen to be very weak in comparison with the 

 ventral. The vagus nerves {vn) arise from the internal border of the ventral 

 lobes and are soon joined in the vagus commissure (cv), back of which they sepa- 

 rate widely to pass to the borders of the mouth ; x 6. 



Figure 9. — Part of a transverse section through the head in the region of the brain, 

 to show the ventral commissure (be) of the cephaUc lacunae {cl). In the section 

 the single lacuna is horse-shoe shaped, surrounding the proboscis-sheath {ps) ; 

 x 10. 



Plate XI. 



Figure 1. — Transverse section through the body- wall in the middle third of the 

 oesophagal region, a short distance below the lateral cord ; e, epithelium ; ew, 

 epithelial musculature consisting of an outer circular, and an inner longitudinal 

 layer ; cw, outer portion of cutis with tubular glands and longitudinal muscles ; 

 cu% inner portion of cutis made up of anastomosing radial fibres; gd, gelatinous 

 tissue filling the "space between the oesophagus and the body- wall ; m, muscula- 

 ture of oesophagus ; x 90. 



Figure 2. — Horizontal section through the head, to show the attachment of the pro- 

 boscis at X. The proboscis is partially everted, so that the walls of rhynchodasum 

 are widely separated and the cephalic lacunae {cl) are much flattened out ; Is, pos- 

 terior end of cephalic slit from which the ciliated canal passes into the side-organ. 

 The cephalic lacunae are seen to pass directly into the lateral lacuna {II) surround- 

 ing the side-organ {so) ; x 18. Compare Plate XII, fig. 1, in which the proboscis 

 lies in its normal position. 



Figure 3. — Part of a transverse section through the nephridial region to show one of 

 the two efferent ducts {ue) of the nephridial system. The main longitudinal canal 

 {u) is seen internal to the lateral cord {Ic)] x 15. 



Trans. Conn. Acad., Yol. IX. June, 1895. 



35 



