ZOOLOGY" AND BOTANY, MICROSCOPY, ETC. 25 



of teeth usually stated to occur in Fishes, tlio pterygo-vomerinc row 

 and the premuxillo-maxillary row, he believes that the former alono is 

 present below the Teleostean-like Ganoid Amia. The so-called maxil- 

 lary teeth of Lepidosteus and Polypterus he believes to be dcrmo-palatine 

 in origin, and he therefore considers that there is in these fish a new 

 arch, formed by the premaxillary and dermo-palatine teeth, which is 

 apparently the arch found in Amphibians and higher Vertebrates. 

 Further, he states that maxillary and mandibular breathing valves are 

 very generally found in all fishes which have a premaxillary bone, and 

 that in Polypterus bones related to teeth are developed in what are 

 apparently the homologues of both breathing valves. " The maxillary 

 breathing valve bone, so developed, forms a second superficial bony layer 

 on the roof of the mouth-cavity, and it and the valve itself seem to foretell 

 the secondary palate of the higher vertebrates." 



Nephrostomes and Segmental Canals in Selachians. * — Frederic 

 Guitel, following up his discovery that Flemming's liquid differentiates 

 nephrostomes from the peritoneum, has made a series of observations on 

 Selachians in the hope of finding these structures. In a female of 

 Squatina angelus, females of Scyllium canicula, and young males of the 

 same species, females and young males of Scyllium catulus, and young 

 females of Centrina salviani, he has succeeded in demonstrating the 

 occurrence of ciliated nephrostomes opening into distinct segmental 

 canals. The number of these varies within the limits of the species, and 

 generally speaking both organs degenerate, especially in the males, as 

 age increases. This process of degeneration attacks the segmental 

 canals first, beginning at the renal end, and travelling outwards towards 

 the nephrostome. Nevertheless, in adult females of Scyllium canicula 

 the organs were found to be large, and seemed to be of functional im- 

 portance, as is indicated by the fact that the segmental canals took up 

 sepia introduced into the ccelom. In a number of other Selachians no 

 nephrostomes could be made out. 



New Abyssal Fish, f — M. Louis Dollo describes as Cryodraco 

 antarcticus g. et sp. n. a fish taken by the Belgian Antarctic Expedition, 

 which appears to be a member of the Trachinidae adapted for life at 

 great depths. Among its remarkable adaptive characters are, the 

 characters of the skin, which is scaleless, colourless, and transparent ; 

 the great elongation of the body ; the spathulate snout ; the great size 

 of the eyes ; and especially the remarkable characters of the ventral fin, 

 which has two united rays of great extent, spathulate at their extremities. 

 This last character is also present in other unrelated abyssal fish, e. g. 

 Bathypterois and Photostomias. Another point of importance about the 

 capture is that it is a new proof of the frequency of the Trachinidae 

 within or in the vicinity of the Antarctic Polar Circle, while the family 

 is hardly known from the Arctic region. 



Development of Pigment.* — S. Prowazek finds that in young fish 

 the different pigment-cells appear in a definite order, first the black, then 

 the red, finally the yellow. Also, the pigment-cells tend to take up 



* Arch. Zool. Exper., viii. (1900) pp. 33-40. 

 t Bull. Acad. Sci. Belg., 1900, pp. 128-37. 

 X Zool. Anzeig., xxiii. (1900) pp. 477-SO. 



