ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 19 



thus the third gill-pocket developes between the fifth and sixth myo- 

 tomes ; but this fact does not prove that the branchiomerism in Ammo- 

 ■ccetes is different from the mesomerism ; the dismetamerism is due 

 merely to the exigencies of space in the embryo. The origin of the 

 nerves, and their relation^to somites, gill-arches, and gill-pockets, is then 

 described in detail. The position of the first spinal ganglion shows that 

 the head consists of six primary head-somites. The inter-somital clefts 

 correspond above to the dorsal cephalic ganglia, and below to the gill- 

 slits, although the latter have lost their primitive topographical re- 

 lations. In other animals, secondary somites may be added to the six 

 primary ones, but there is no fundamental difference between primary 

 and secondary cephalic somites. There is an almost exact numerical and 

 topographical agreement between neuromeres and somites. 



Skull of Kestrel.* — Herr P. P. Suschkin gives an account of the 

 development and structure of the skull in Tinnunculus, Besides contri- 

 butions to our knowledge of the morphology of the bird's skull in 

 general, and of falcons in particular, the memoir includes an interesting 

 contrast of the development of the falcon with that of the chick. In the 

 former there is slower development in the early stages, and palingenetic 

 phenomena, e.g. the independent primordium of the trabeculse and the 

 retention of four pairs of " cranial ribs," are observed, which have beea 

 lost in the chick. In the later stages the development is relatively more 

 rapid than in the chick. For the preservation of palingenetic traces a 

 prolonged development is essential. 



Development of Ductus Endolymphaticus.f — Prof. Kiebel quotes 

 various authors (Netto, Poli) whose observations seem to disprove 

 Hertwig's view that the ductus endolymphaticus represents the connec- 

 tion between ear and epidermis in Selachians, and so the last remnant 

 of the ectodermal invagination which produces the ear-vesicle ; and then 

 figures a chick section which shows clearly a cord of cells connectiug 

 the developing ductus with the ectoderm. His sections prove that this 

 *cord of cells is the last remnant of the primitive connection between the 

 ear-vesicle and its place of origin, and thus confirm Hertwig's views in 

 all respects. He believes that the apparent absence of the connection 

 between ductus and ectoderm in some Vertebrates is in all cases due to 

 a hastening of events, the ear-vesicle being separated from the ectoderm 

 long before the ductus originates. 



Pads on the Palm and Sole of the Human Foatus.J — Mr. R. H. 

 Johnson has studied these, and comes to three conclusions: — (1) There 

 are, on the sole of the human foetus of 2-3 months, four mounds situ- 

 ated, interdigitally along the line of the metatarso-phalangeal joints. 

 Three mounds exist in a similar situation on the palm. On the foot the 

 mounds disappear ; on the hand they persist as the less definite " mounts " 

 of palmistry. (2) These mounds are homologous with the walkiug pads 

 of some mammals, and have a direct relation to the " centres of dis- 

 turbance " of the epidermic ridges on the palms and soles of man and 

 other Primates. (3) Corresponding with a poorer development of these 



* Nouv. Mem. Soc. Imp. Nat. Moscou, xvi. (1899) pp. 1-163 (6 pis.), 

 t Anat. Anzeig., xvi. (1899) pp. 490-2 (1 fig.). 

 X Amer. Nat, xxxiii. (1899) pp. 729-34 (6 figs.). 



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