ZOOLOGY AND BOTANY, MICKOSCOPY, ETC, 875 



roomy aquaria. In five of the vessels the brood consisted entirely of 

 females ; in six more the proportion of the same sex was from 91 • 5 to 

 96 per cent. In but two aquaria was any considerable number of males 

 produced, viz. 13 per cent, in the one, and 28 per cent, in the other ; 

 whereas in nature the number of males is about the same as that of 

 females. The cause of this phenomenon appears to be that artificial 

 conditions tend, by the smaller quantity of food thus supplied, to 

 favour the develoj)ment of the weaker sex, which thus predominated ; 

 this view is enforced by the circumstance that the aquarium in which the 

 greatest number of males was produced, had been accidentally inundated 

 with muddy water, which probably contained a large amount of nutri- 

 ment in the form of minute organisms, such as Eotifera, Infusoria, 

 and Algfe, by which encouragement was given to the development of 

 the stronger sex. This result is the converse of that arrived at by 

 Prof. Hoffmann, of Giessen, who found that deficiency of nourish- 

 ment resulted, in the case of plants, in the production of an excess of 

 males. 



Cochlea of the Monotremata.* — Dr. Urban Pritchard has been 

 enabled to extend his investigations into the minute structure of this 

 organ by an examination of OrnithorJiyncJius platypus. The cochlea 

 is a somewhat curved tube, about ^ inch in length, and Jg. inch in 

 diameter ; when compared with that of typical Mammals and of Birds 

 we find that it has much more resemblance to the latter. Thus the 

 cochlea of both Duckbill and Bird consist of curved tubes, enlarged 

 at their anterior extremities, with not much difference throughout 

 except at their apex. On the other hand, when we come to examine 

 the interior its agreement with the Mammalian type is well marked ; 

 the chief differences appear to be that in Platypus the scala vestihuli 

 is throughout larger than the scala tympani, whereas in the typical 

 Mammal the two are, for the most part, much of the same size. In 

 the membrane of Eeissner the epithelial cells are thicker than in the 

 typical cochlea, but there is, in addition, another point of difference 

 in the presence of " blood-vessels running across the membrane from 

 lamina to ligament, forming here and there convoluted knots ; " these 

 seem to have never yet been observed. The organ of Corti has much the 

 usual characters, but the rods stand more upright, and the extremities 

 are not so well developed. The author has not been able " to make 

 even an approximate calculation of the number of rods or bristle 

 cells, but there must be a much fewer number of these in the duck- 

 bill's cochlea than in that of the ordinary mammal." The presence of 

 a lagena at the end of the Monotrematous cochlea is a curious point, 

 which, while showing a resemblance to the Bird is, as the author 

 reminds us, "a link between the cochlea of the higher and lower 

 Vertebrates, and not merely between that of the Mammal and Bird." 



On the whole, then, the organ of Corti is not nearly so extensive 

 as in typical Mammals, and the various minute structures of which it 

 is made up, do not seem to be so well developed. 



* Phil. Trans, clxxii. (1881) pp. 267-82 (1 pi.). 



