ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 403 



the olfactory sac, the lens, and the auditory vesicle, in the various 

 Vertebrate types, and observes that two deviations from the norm are 

 not infrequent, probably because of differences in the spatial and other 

 conditions of development. 



Instead of an invagination whose margins coalesce, there may be a 

 solid primordium, which subsequently acquires a lumen by dehiscence. 

 An organ may thus owe its origin entirely to the inner ectoclermic layer, 

 while the outer layer, which normally stared in the development, has no 

 share beyond being protective. Origin by infolding and origin from a 

 solid primordium are not rigidly separable, for intermediate modes 

 occur, aud both may occur in one type. 



Development of Immature Ova of Rana fusca.* — E. Bataillon 

 experimented with ova removed from the female towards the end of 

 copulation, when many were still in the body cavity. These were 

 fertilised and the segmentation was observed. Apart from a few irregu- 

 larities, the development seemed at first almost normal. But some eggs, 

 apparently undeveloped but with slightly dilated volume, were seen 

 moving actively and regularly within their envelopes. These monstres 

 ankles showed a rudiment of a blastula-like nature, a complete cover- 

 ing of ectoderm, a large segmentation-cavity, not a trace of invagination, 

 but a cylindrical prolongation towards the region of the blastopore. 



In another set, two kinds of abnormality were observed — (a) witli 

 cleavage restricted to the animal hemisphere, with nuclear division 

 "without cell-boundaries at the lower-pole ; and (b) with no cell-boun- 

 daries at all, but numerous nuclei. 



The author thinks that all the different cases may be arranged in a 

 series ; during maturation there are oscillations in osmotic pressure, aud 

 there is a gradation in the results. There may be no true cell-division 

 except at the upper pole, and karyokinesis only below; there may be no 

 true cell-division at all, and abnormal karyokinesis ; or there may be no 

 physical obstacle operative until the time of gastrulation approaches, and 

 then there result the exogastrulse (like Lithiuni-larvas of Echinoids) or 

 monstres anides referred to above. 



Somatopleure and Splanchnopleure. f — Prof. Charles Sedgwick 

 Minot protests against the frequent German misuse of these terms as 

 equivalent to somatic and splanchnic mesoderm. Sir Michael Foster, 

 who invented the words, writes " Certainly somatopleure is body-wall, 

 both ectoderm (epiblast) and mesoderm (mesoblast), and splanchnopleui'e 

 to suit." It was to this sense that Huxley and Balfour adhered, and it 

 is to this sense that all should adhere. There are many terminological 

 difficulties which seem inevitable, but this new ambiguity is altogether 

 unnecessary. 



Female TJrmogenital Organs of Marsupialia. J — J. P. Hill finds 

 that in Myrmecobius faseiatus the female urinogenital organs agree 

 with those of Peramcles in the possession of a small median vaginal 

 apparatus, consisting in virgin animals of two separate cul-de-sacs, and 

 also in that the anterior parts of the lateral vagin$e, the uterine necks, 



* Coraptes Reridus, cxxxii. (1901) pp. 1134-6. 



t Anat. Anzeig., xix. (1901) pp. 203-5. 



j Proc. Liim. Soc. N. S. Wales, xxv. (1900) pp. 519-32 (3 pis.). 



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