THE OOLOGIST. 



31 



four weeks. Unless a very uniform de- 

 gree of heat is applied, it requires eggs in- 

 cubated artificially somewhat longer. 



It is needless here to enter into a minute 

 explanation of the progress of development 

 of the embryo, as that has already been 

 fully detailed and illustrated by several au- 

 thors ; but an outline of the stages of incu- 

 bation, however, may to the interested, be 

 of advantage : In the center of the yolk, 

 enclosed in a little sac called by scientists 

 the memhrana vitelli, is the germ or fu- 

 ture chick. The warmth imparted to the 

 egg calls the germ into activity, and though 

 gradual, the progress of its development is 

 :ery rapid. Until about two days after in- 

 cubation is commenced, all that appears to 

 the naked eye are numerous small blood- 

 vessels and a globular mass of yellowish 

 substance, which eventually forms the em- 

 bryo. This soon takes shape, and on the 

 third and fourth days the embryo is pos- 

 sessed of recognizable form but is still im- 

 perfect, the head and eyes apparently being 

 farthest advanced. The albumen now be- 

 gins to assume a neutral position, and on 

 the fifth and sixth days the forming bones 

 of the chick obtain strength. The shell 

 being always permeable by air, during the 

 process of incubation admits a certain quan- 

 tity to the space at the larger end of the 

 egg. Consisting largely of oxygen, the air 

 of this space rapidly expands and stipplies 

 the embryo in its confinement. The de- 

 velopment of the head is most rapid, the 

 brain, nerves, and vascular portions being 

 distinguishable long before the feet and 

 wings are formed. From the sixth to the 

 tenth day, the muscles and quill feathers 

 begin to form, and from this time the feath- 

 ers, bill, and claws rapidly gain strength, 

 until at the exit of the chick their shape is 

 almost entirely developed. The chick is 

 not assisted in freeing itself from the shell 

 by its parents, but eifects its own libera- 

 tion. How the release from the shell is 

 accomplished* has been copiously discussed 

 in a previous issue of this journal, and re- 



* Vide pages 51, 59 and 63 of Vol. II. 



quires no supplementary details. Birds who 

 deposit their eggs with regularity rarely fail 

 to produce the full number of young, i. €., 

 to hatch every egg. The young generally 

 remain in the nest until able to fly ; but 

 some species, the Sandpipers, Ducks, etc., 

 leave the nest as soon as hatched, and are 

 immediately possessed with the power of 

 running or swimming. As a rule, the young 

 are not clothed in full plumage until the fol- 

 lowing year. 



The nest is not always occupied a second 

 time ; indeed, the greater number of birds 

 build a new nest every year, and a large 

 number of those which raise two bi'oods in 

 a season construct two different nests. Most 

 birds of prey simply repair and add to the 

 structure of the preceding year, but all spe- 

 cies if not disturbed, will with their young 

 nest in the same locality year after year, 

 and one wdll often find within an area of 

 two or three rods perhaps a dozen Vireos' 

 nests. 



JIoiv our Journal is Appreciated. 



It gives us pleasure to note the interest 

 taken in Thk Oologist, and we cannot re- 

 frain from presenting some of the compli- 

 mentary notices we have received. Wm. 

 Brewster, Esq., of Cambridge, says: 



i "I am very much pleased with your publi- 

 cation and heartily wish it the success that it 

 ; so fully merits." 



i Mr. D. 8. Bryant of San Francisco, an 

 j enthusiastic naturalist, writes : 



" It is j ust what our young naturalists want . 

 You will get new subscribers from Oakland." 



Mr. C. J. Maynard, of Newtonville, 

 Mass. , writes us : 



"I have with great pleasure observed the 

 steady improvement in your little journal. 

 You have now arrived at a point where it is 



truly deserving of praise." 



i 

 Were it not for space, we should pub- 

 lish others, all of which are reflected in the 

 above few testimonials. 



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