HARDWICKE'S SCIENCE-GOSSIP. 



53 



oblonga (?). These were very minute and indistinct ; 

 rather rare. Biloadina ringens: this is a most 

 beautiful and perfect specimen ; it is of a white 

 colour and middle size. Rare. Spiroloculina canalicu- 

 lata, D'Orb. (fig. 37). Two perfect examples of 

 this species were found, showing the character of the 

 genus well. Small and rare. 



In this short paper I have endeavoured to give an 

 idea of the character of the Foraminifera found at 

 Shetland. I have not given all the species found 

 there, and only those that I possess myself. I have 

 drawn the figures myself, without the aid of the 

 camera lucida. In my research among this bit of 

 sand I find that nearly all of the Foraminifera are of 



Fig. 37. Spiroloc2iliua canalicidata ; nat. size, J 3 in. 



Fig. 38. Biloculina ringens; nat. size, J 3 in. 



Fig. 39. Truncatulina loba- 

 tula ; nat. size, ^ in. 



Fig. 40. Ditto, other side. 



NOTES ON THE DEVELOPMENT OF 

 FROG'S SPAWN. 



By A. M. M'Aldowie, M.B., 



Member of the North Staffordshire Naturalists' Field Club. 



PROBABLY no animal is better known, from an 

 anatomical and physiological point of view, 

 than the Common Frog. Developmentally the frog 

 has been specially studied, on account of the inte- 

 resting metamorphoses through which it passes before 

 it arrives at maturity, and also on account of the 

 advantages which its egg offers for the examination 

 of the ovum, the transparent albuminous covering 

 affording unrivalled facilities for observations on, and 

 experimental investigation into, the subject of deve- 

 lopment. The microscopic structure and changes 



a brownish colour, showing that the water is impreg- 

 nated with oxide of iron ; also that the Globigerina 

 are dwarfed and thin, owing to the shallowness of the 

 water, 120 fathoms, whilst the same species from 

 the Atlantic, at a depth of 1,450 fathoms, are larger 

 and more bulky. And this gives the fact that the 

 Globigerina grow larger and more bulky in deep water, 

 whilst they are dwarfed and thin in shallow water. 

 Attercliffe, Sheffield. . 



Fig. 41. Frog's Spawn ; 

 nat. size, March. 



Fig. 42. Ditto, 

 April 4th. 



Fig. 43. Ditto, April Sth ; 



dorsal aspect ; lateral 



aspect. 



44. Ditto, April nth; 

 dorsal aspect ; lateral 

 aspect. 



which are observed during the development of the 

 embryo of the frog, are described and figured in 

 most text-books of comparative physiology and his- 

 tology, but the ordinary naked eye appearances and 

 modifications which it exhibits are not to be found in 

 these works. Nearly all zoological manuals give a 

 series of illustrations representing the various stages 

 in the development of the tadpole after its escape 

 from the egg, but they do not figure the alterations 

 which take place previously, without which the series 

 cannot be considered complete. St. George Mivart, 

 although he details the process of yolk subdivision 

 and cleavage, and the other microscopic changes 

 through which the embryo passes, yet with regard to 

 the naked eye appearances he merely states,* "Gra- 

 dually the embiyo assumes the form of a young tad- 

 pole, and is provided with a pair of little ' holders ' 

 (or organs for adhesion), just behind the mouth, with 

 six openings on each side of the neck, and with a 

 pair of rudimentaiy external gills. " Huxley, in what 

 is undoubtedly the best work on the frog extant, in 

 reference to this subject says,f "While still within 

 the egg the embryo assumes the form of a minute 

 fish, devoid of limbs and with only rudiments of gills, 

 but provided with two adhesive discs on the ventral 



* The Common Frog (Nature Series), 1874, p. 15. 

 t Elementary Biology, 1875, p. 155. 



