ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 155 



function. The otoliths of Mammals are usually small, but in the 

 porpoise, seal, and kangaroo this is not the case. 



Teeth-formulae of Platyrrhine and Catarrhine Primates.* — L. 

 Bolk suggests that the catarrhine set of teeth has not originated by an 

 excalation but by a terminal reduction. He is convinced that because 

 Mo, has become M^, the replacing tooth, which originally belonged to it, 

 namely P3, no longer appears. In any case, this investigation shows 

 that the differentiation of the entire set of teeth of the Primates is more 

 intricate than was hitherto supposed. 



Lachrymal Bone of Ungulates.! — Theodor Knottnerus-Meyer has 

 made an elal^orate study of the characters of the lachrymal bone in 

 Hyracoidea, Proboscidea, Perissodactyla, and Artiodactyla, and shows 

 that this may be of great service in determining systematic relationships. 



Mandibular Articulation in Monotremes.| — W. Lubosch has made 

 a comparative study of the mandibular articulation in Mammals, with 

 particular reference to the Monotremes. The characteristic mammalian 

 articulation arose in Triassic ages in an association of dentary and 

 squamosal. As the skull became arched above, the squamosal was dis- 

 placed downwards, and with this were associated the development of 

 the intertempoi-al bone and the shunting of the ear, besides modifica- 

 tions of the pterygoid and hard palate. The primitive mucous pocket 

 between the periosteal surfaces of squamosal and dentary was abetted 

 by co-operation on the part of Meckel's cartilage (a bud of which grew 

 in below the dentary to the joint-surface), and perhaps by co-operation 

 of the petrosal, similarly sinking into the squamosal. The periosteum 

 of the joint was modified, the pterygoideus externus was associated 

 therewith. In the Eocene ages there was a marked differentiation. 

 The duckmole is an offshoot from a rodent-like Monotreme stock. The 

 joint-surface was modified ; there was a reduction of the loose connec- 

 tive tissue and a regularly arranged modified periosteum, with which the 

 external pterygoid lost its previous connection. From a non-specialised 

 Monotreme condition, the state of affairs in Echidna arose. The inser- 

 tion of a median portion of the external pterygoid in the modified 

 periosteum is of phyletic importance. Gradually a free meniscus was 

 formed, 



Preen-Gland of Birds.§— P. Paris gives a useful account of the 

 " uropygal " gland. It is always bilobed, but the lobes may be more 

 or less fused ; each lobe has a canal, but the two canals have a common 

 aperture. Its occurrence is rather difficult to interpret, for it is absent 

 in some birds and present in their near relatives. It is usually best 

 developed in birds which frequent water, but while it is large in the 

 white stork, it is small in the herons. Kossmann's conclusion that the 

 excretory papilla is adapted to the form of its possessor's beak, is not 

 well borne out by the facts. 



Three types are distinguished : — (1) With lobes coalesced, with a 



* Proc. Section of Sciences Acad. Amsterdam, viii. (1906) pp. 781-93. 

 t Arch. Naturges., Ixxiii. (1907) pp. 1-152 (5 pis. and 34 figs.). 

 X Jen. Zeitschr. Naturw.. xli. (1906) pp. 549-606 (4 pis. and 5 figs.). 

 § Bull. Soc. Zool. France, xxxi. (1906) pp. 101-7 (24 figs.). 



