136 



THE; YOUNG 



NATURALIST. 



to be derived from the middle germinal 

 layer (mesoblast) of the blastoderm, which, 

 consisting at first of colourless nucleated 

 cells, become differentiated, losing their 

 nucleus and developing pigment in their 

 interior. In the adult, matters are at vari- 

 ance, one observer believing one thing and 

 another another. There seems, from the 

 observations of various authors, to be four 

 chief sources : — 



(1) From the white corpuscles. 



(2) In the marrow of bone. 



(3) In the spleen (?). 



(4) From the corpuscles of Zimmermann. 



The red medulla of bone appears to be 

 accepted by the best authorities to be the 

 most probable birthplace of the red corpus- 

 cles, as transitional forms between them 

 and the marrow cells have been described 

 by Neumann, Bizzozero and Schafer. "The 

 marrow cells, which are very like large pale 

 blood-corpuscles, but with a less granular 

 protoplasm and a larger, more distinct 

 nucleus, acquire a reddish tinge in conse- 

 quence of the formation of haemoglobin in 

 the protoplasm. The colour becomes grad- 

 ually more pronounced, and soon it is found 

 that it is confined to a part only of the pro- 

 toplasm. Presently the coloured protoplasm 

 gradually becomes separated from the rest 

 of the cell, and forms a red corpuscle, which 

 is at first cup-shaped, but afterwards be- 

 comes moulded in the circulation to form a 

 bi-concave disc." (Schafer on Quains Anato- 

 my) The spleen, until lately, was thought to 

 form the red corpuscles, but this has been 

 supplanted by the view of Holliker, who has 

 conclusively shown th at large numbers of 

 these bodies can be seen in various stages of 

 disintegration. The red medulla of bone 

 then, as far as our researches have as yet 

 taken us, seems to be the probable birth- 

 place of the red corpuscles, and the spleen 

 their graveyard. 



Middlesex Hospital. W. 



IN-DOOR 

 NATURAL HISTORY. 



By Albert H. Waters, B.A. 



VIVARIA. 



Reptile Vivaria. — Some kinds of rep- 

 tiles do very well in a fern case, but I think 

 a shallow box, with a glass lid to it, is the 

 most convenient for feeding purposes, and 

 the broader it is the better. For lizards the 

 ends should be of wire gauze or perforated 

 zinc, and the bottom should be covered 

 about an inch deep with fine sand, and a 

 little moss may be introduced with advan- 

 tage. Smooth newts (Lophinus punctatus) 

 may be kept in a fern case, as they like a 

 humid atmosphere, but a broad and shallow 

 box is best for them also. This should have 

 a slate bottom and glass sides, the edges of 

 which are cemented with white lead, red 

 lead, and litharge; the glass need not be 

 thick, as it is not intended to hold water. 



Insect Vavaria. — Butterflies and moths 

 require abundance of air, and they soon die if 

 this be denied them. An arrangement simi- 

 lar to a larva breeding cage with gauze on 

 all sides would suit them best, but as, of 

 course, we wish to see them plainly, glass 

 cannot be dispensed with ; the vivarium 

 therefore must be so constructed that, al- 

 though glass be largely used, a free circu- 

 lation of air may take place. This, how- 

 ever, is easy. Imagine a wide fern case 

 with the back and front of glass, with the 

 exception of six inches, or so of the lower 

 part, and the sides and top of wire gauze* 

 and the portion of the back and front just 

 mentioned (namely about six inches of it), 

 of perforated zinc, in which is one or more 

 doors for convenience of introducing insects, 

 &c, and you have an arrangement such as 

 will answer admirably. The front pane of 

 glass should be set in a frame, with hinges 

 and catch, so that it may be opened when 

 required, to place inside vases oi flowers, 



