George W. Bartelmez f,- 



rather infrequently, since a sero-albuminous fluid iMcdominaics. With 

 increasing size the yolk becomes more yellow, uiiiil in the lully ma- 

 ture egg it has attained almost a golden color. The yolk in the mature 

 ovule, and while it is still in the beginning of the oviduct, is found to 

 be much more viscid and cohesive than it was previously and than it 

 afterwards becomes while the albumen is being laid down; perhaps 

 it takes up some of the fluid of the latter/"' Even at the time when an 

 ovule begins to grow yellow, there may be recognized at its center a 

 whiter and more fluid material such as you will And rather closelv 

 [ 7 ] resembles the cicatricula in mature ovules. This white yolk material 

 is best seen for the first time in laid eggs.""' It is this no doubt which 

 in its time gave rise to the problem of Bellini,* for it is found not only 

 in boiled eggs but also in the very freshest and in every ovule from the 

 time that it becomes clearly visible. Thus, when you have cut off 

 parts of the yolk under water with a pair of Cowper's scissors, begin- 

 ning at the cicatricula, the fresh surface exhibits three concentric 

 zones of different colors;"" the outer of these is rather pale, the middle 

 a deeper yellow, the inner again paler surrounding the latebra of more 

 fluid white material. This fluid is situated at the center and appears 

 to send out a delicate canal toward the middle of the cicatriculaf 

 (figs. i6-i8). 



At all events this white center with concentric strata surrounding 



* [This footnote was added in the 1830 edition, but the "problem of Belhni" is dis- 

 cussed in the 1st edition.] See Laur. Belhni: Opuscula aliquot ad Archibald. Pit- 

 carnium, Lugd. Bat., 1714. p. 14: and further: Comment. Bonouiens. \o\. II, Pt. I, 

 p. 85; Pt. II, p. 369 and following; Comm. Pauli Bapt. Balbi de lielliniauo prob- 

 lemate; also Miscell. soc. Taurinerts. Vol. I, p. 3 and following in Commentario 

 Joannis Franc. Cigna, who was the first to refute Bellini in the matter of the 

 cicatricula of boiled eggs.<"> 



[The first of these references is to an "opuscuhim" addressed to Archibald Pit- 

 cairn in 1693, namely De motu cordis intra & extra utcrum. Bellini's great discovery 

 is set fortli on p. 112 of the Opera Omnia, Part II (cd. of 1708). 



Balbi's contribution occurs in De Bononiensi Scienliariim et .irtinum Institulo 

 atqiie Academia commentarii. 1731. 



Cigna's refutation of Bellini is in Miscellanea pliilosophico-mathematica Socie- 

 tatis Privalae Taiirinensis, Vol. I: "De Belliniano jjroblcmati sen de ovorum elixa- 

 torum cicatricula."] 



t [Footnote added in 1830.] Later investigations have raised doubts in my mind 

 concerning this structure. Von Baer, to be sure, in his work {Ueber die Entwicke- 

 lungsgeschichte der Thiere, Erster Theil, Konigsbcrg, 1828) has applied our ob- 

 servations on the central latebra of the yolk to his theory of halos,^^> but whether 

 he has confirmed it by his own observations does not appear in any published work. 

 Unless the arrangement of the chalazae and their firm attachment to the volk by 

 the intervening membrane of Dutrochet suffices to explain the constant position of 

 the cicatricula at the upper surface, I should .say that the central fluid with its 

 canaliculus extending to the cicatricula acts like a plumb line so that the yolk, 

 tending of its own accord to rise upward within the mass of albumen is prevented 

 from further rolling so that the cicatricula always preserves the same position 

 uppermost. At any rate it can be justly assumed that the watery fluid [of the 

 latebra] has a higher specific gravity than the semiolcaginous substance of the yolk. 



