AMBLYSTOMA PUNCTATUM. 3 



Most of the e^gs were laid flnring the niglit, and by nine o'clock 

 the next morning the first segmentation furrow had nsnally made 

 its ap|iearance. The spermatozoas, Plate 4, Fignre 31, are un- 

 usnally large, averaging .75 millimetre or .03 of an inch in length. 

 The}' are very slender and acutely pointed at both ends. When 

 first thrown out they often have a remnant of the mother-cell still 

 attached to some portion of them, but on account of their active 

 movements it is soon thrown off. As active movements begin to 

 cease in them, one end is often bent around till it touches and 

 adheres lo the body, thus forming a loop of variable shape and 

 dimensions, which has much the appearance, until carefully studied, 

 of an eidargcd portion or "head" of the spermatozooid, Plate 4, 

 Fignre 31c, 31d. For ready reference, I give the measurements of 

 the spermatozoa of a number of different amphibia, both Anoura 

 and Urodela. 



Eana temporaria, 008 to .011 of a mm. 



PHldbiites fuscus, 017 " " 



Triton, 088 " " 



Mennpoma allo£;honionsp, . . . .2.5 " *' 



Amblystoma piinotatiim, . . . .75 " " 



The first three are taken from Wagner and Leuckart's article,* 

 the others were made by myself. 



A few minutes after an egg is deposited there exists between the 

 inner shell or membrane and the yolk, a quantity of gelatinous 

 matter which seems to form, as development goes on, a third, in- 

 most shell, very delicate and hyaline. The yolk lies so close to 

 this inmost shell that it cannot at Hrst be distinguished. As the 

 process of .segmentation begins, the yolk-niass is .separated by a 

 small space from this inmost shell, when the latter becomes dis- 

 tinctly visible. It remains until the medullary folds are nearly 

 closed in, when it disappears; it being often, if not always, torn 

 a])art by the rapidly elongating embryo. At this early period the 

 diameter of the outer shell is about twice that of the inner, and 

 this relative size is maintaine<l with considerable resrularitv throusrh- 

 out the period of intra-oval life. Both shells now rapidlj' increase 

 as water is absorl)ed. By the end of segmentation the shells have 

 reached nearly or quite their largest size, and remain as they then 

 are until the embryo bursts them and makes its way out. 



The Cyol of Anat. and Phjs., f. 472. 



