1894.] XOTjyG OF ECHIDNA ACULEATA. 11 



this is much thicker than the non-sensory epithelium covering the 

 shelf, which is columnar and stratified, and bears especially strong 

 cilia (fig. 16). I was unable to recognize any cilia on the sensory 

 epithelium. The function of " Jacobson's turbinal '" must there- 

 fore be a purely mechanical, and not a sensory one. The sub- 

 epithelial tissue on the dorsal and internal side of the organ 

 encloses large bundles of olfactory nerves, which send branches to 

 the other parts. A number of small gland-tubes are present in 

 the connective tissue of the turbinal, and these open at intervals 

 into the lumen of the organ. 



On the dorsal and lateral side of Jacobson's cartilage a thick 

 mass of tissue is present between it and the epithelium covering 

 the ridge which projects into the nasal cavity and in which the 

 whole organ is enclosed. This tissue contains a number of simple 

 glands, which also extend posteriorly to Jacobson's organ, exter- 

 nally to the more complicated " septal gland," and open at intervals 

 into the nasal cavity (figs. 6-11 and 14-16); the septal gland 

 with its ducts is therefore of great extent, passing along almost 

 the entire length of the nasal chamber. 



The epithelium covering the whole ridge is columnar and 

 ciliated like that lining the general nasal cavity, and passes into 

 stratified pavemeiit-epithelium behind the naso-palatine duct, the 

 latter form extending back still further on the nasal floor. 



Glaud-tubes similar to those just described are also present in 

 great abundance beneath the epithelium of the posterior part of 

 the maxillo-turbinal (=Steno'8 gland?) (figs. 11 and 15), and also 

 to a less extent beneath that of the ethmo-turbinals and other 

 parts of the nasal cavity. 



I do not propose to describe the structure of the eye here, and 

 will only mention that in the youug Echidna it lies some distance 

 from the surface, and a groove, lined by a thick cuticle, extends 

 inwards towards it fi*om the integument. 



In Stage I. the two layers of epithelium bounding this groove 

 join at its base so as to form a solid band connecting the con- 

 junctiva with the epidermis. 



In Stage II. the eyelids are beginning to separate, a narrow 

 slit being present in " their middle part. There is a very large 

 Harderian and a smaller lacrymal gland, and folds of the epithelium 

 of the eyelids apparently represent the developing Meibomian 

 glands. The naso-lacrymal duct (n.d.) opens into the outer side 

 of the nasal chamber rather further back than Stenson's duct, in 

 a bay between the " ali-nasal turbinal " and the floor of the chamber. 

 From this point it extends directly backwards, just outside the 

 nasal capsule, to the conjunctival chamber. 



]S"eglecting theii- more obvious resemblances and differences, 

 and confining ourselves to the observations recorded above, it \m\\ 



