ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 519 



means of conchological comparisons, and the author concludes that the 

 resemblance between the Tanganyika shells and those of the British 

 inferior oolite is not sufficiently close to warrant any theory as to the 

 derivation of the former from the latter, as Moore has suggested. On 

 the other hand, the anatomy of the existing molluscs reveals a peculiarly 

 archaic character, and also a singular blending of attributes usually held 

 to be distinct. These gastropods may, in some way, have had a remote 

 marine origin, although that need not have been Jurassic. The palae- 

 ontological and geological evidence is also reviewed, but from no point 

 of view is much support found for Moore's theory, and the problem in 

 its main features remains unsolved. 



Food of Fishes, Birds and Insects* — S. A. Forbes gives a very 

 exhaustive account of the food of young and adult fishes and birds of 

 the State of Illinois. The paper is illustrated by numerous tables in 

 which the "food" for each species treated is classified, and the pro- 

 portions indicated. In the case of the birds, the food of each month is 

 separately shown. In studying the food of birds, the author found it 

 necessary to construct a key to the genera of the Carabidae (based 

 primarily upon the mouth structures), an outline of which he gives. 

 Notes on the food of these insects are also sriven. 



&* 



Phototropism of Convoluta and Nereids.f — G. Bohn has experi- 

 mented with these forms, and finds that there is no phototropism such 

 as Gamble and Keble asserted. The- animals move indifferently from 

 light to shadow and vice versa. There is a tendency to aggregate in the 

 line of shadow just beyond the light, but this is done by those coming 

 from the light and suffering from light-fatigue. The character of the 

 water, whether salt and deep, brackish, etc., also affects their behaviour. 



Dermal Fin-Rays of Fishes.J — Edwin S. Goodrich has studied these 

 in numerous types. In all the fins of the true Pisces there are dermal 

 rays of mesoblastic origin, the Dermatrichia ; but in adult living fishes 

 there are four of these : 



1. In the Elasmobranchii and Holocephali, and probably also in the 

 Acanthodii and Ichthyotomi, these rays are unjointed, occasionally 

 branched and composed of a fibrous substance of horny consistence 

 without bone-cells. When placoid scales are present, they are quite in- 

 dependent of the rays and more superficial. The author calls these rays 

 " Ceratotrkhia." Their origin is unknown, but for the present they 

 must be considered as special developments of the connective tissue. 



2. All living ' Teleosto rues' — that is to say, Polypterus (Calamo- 

 ichthys ?) and the Actinopterygii (Ganoids and Teleosts) — are provided 

 with small, horny, unjointed rays at the edge of their fins, to which the 

 name " Actinotrichia " has been given. In the early stages of development 

 these are the only dermal rays supporting the fins. They were probably 

 present in the extinct Actinopterygii and Crossopterygii. They appear 

 to be vestigial structures homologous with the ceratotrichia. 



* Bull. Illinois State Lab. Nat. Hist., i. (1903) pp. 19-176. 



t Comptes Rendus, cxxxviii. (1903) pp. 1292-4. 



% Quart. Journ. Micr. Sci., xlvii. (1904) pp. 465-522 (6 pis. and 6 figs.). 



