ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 577 



immediate aim was to test embryologically the evidence, based upon 

 anatomical considerations, for certain supposedly Elasmobranch and 

 Amphibian characters seen in the adult vascular system of Cera I ml us. 

 The embryological evidence has necessitated continual subtraction from 

 the list of real Elasmobranch resemblances, and continual addition to 

 the list of Amphibian characters. The author gives a useful summary 

 of the Amphibian resemblances, of the characters more or less inter- 

 mediate between Elasmobranch and Amphibian arrangements, and of 

 the characters peculiar to Ceratodus, and he concludes that it is im- 

 possible to believe that the Amphibian resemblances seen in Ceratodus 

 in the development of the vascular, respiratory, and urinogenital systems, 

 as well as throughout the early processes of development, are of the 

 nature of parallelisms. In the light of their embryology, it is im- 

 possible to believe that the Dipnoi and the Amphibians are not closely 

 related, and that they have not travelled for a time along the same 

 path at some period during their history. 



Development of Olfactory Organ of Lamprey.* — W. Lubosch 

 gives a full account of the development and structure of the larval 

 olfactory organ in Petromyzon planeri, and follows its metamorphosis 

 and the development of the rudimentary olfactory sacs. He shows 

 that the so-called " septum " is foreign to the primitive anlage of the 

 olfactory organ, being really a region of the dorsal wall of the nasal 

 passage which is imported into the complex of the olfactory organ 

 proper. The formation of the so-called " folds " is due to the forma- 

 tion of new olfactory sacs. It is probable that the so-called " glands " 

 appended to the olfactory sacs are degenerate portions of the olfactory 

 organ, perhaps hints of an ancestral distal extension. The author 

 maintains after full discussion that a paired element is pre-formed in the 

 unpaired olfactory plakode, and that the larvae pass through a " protam- 

 phirrhinal " and a " mesamphirrhinal " stage until a " metamphirrbinal " 

 condition is attained. He also contends that the olfactory mucous 

 membrane of the lamprey is to be regarded as the sum of different 

 plakodes, each representing an ancestral sensory organ. 



Closure of Nasal Apertures in Human Embryo.f — G. Retzius calls 

 attention to the fact that between the 3rd and 5th month the external 

 nares of the human foetus are closed by a coherent epithelial tissue 

 which projects from the openings. K. Peter notes that in reptiles and 

 birds the epithelial walls simply fuse together, while in mammals there 

 is proliferation. Other openings — e.g. eye, urethra, rectum— may be 

 ■closed, as if the delicate epithelium required to be preserved from sur- 

 rounding fluids. 



Sixth Branchial Pouches in Amphibians.t — A. Greil finds that 

 there is a transitory sixth pair of branchial pouches both in Urodela 

 and Anura, and that it has no relation to the thymus. From the 

 ventral median portion there rises an epithelial bud, first solid and 

 afterwards with a lumen, which becomes the "post-branchial' 1 and 



* Jenaische Zeitschr. f. Wiss., xl. (1905) pp. 95-148 (2 pis. and 14 Bg8.). 

 t Verh. Anat. Ges., 1904 ; Anat. Anzeig.. xxv.. Krganzuugslieft, pp. 43-4. 

 J Tom. cit., pp. 136-7 (1 fig). 



