803 
wieder, wie ich dies auch bei den Schlangen und Eidechsen nachge- 
wiesen habe. 
10) Die in Rede stehenden Wahrnehmungen bestätigen die Sup- 
dositionen über den vermutlichen Ursprung der Thymus und der 
epithelialen Rudimente in der Halsgegend, welche ich bei der ana- 
tomischen Untersuchung junger Schildkröten angetroffen und in einer 
früheren Arbeit (Beiträge zur Kenntnis der Halsgegend bei Reptilien, 
I. Anatomischer Teil, veröffentlicht in: Bijdragen tot de Dierkunde, 
uitgegeven door het Genootschap Natura Artis Magistra te Amsterdam, 
1880) schon hervorgehoben habe. 
Nachdruck verboten. 
Experimental Studies on the Teleost Eggs. 
(Preliminary Communication.) 
By T. H. Morean, Associate Professor Biology, Bryn Mawr College. 
I have sought to work out experimentally on the eggs of the fish, 
two problems. First, I have applied to this typically meroblastic egg, 
the experimental methods used by PFLÜGER, Roux, CHABRY and DRIESCH. 
Secondly I have tried to test by experiment the theory of concrescence 
of the embryo. Very definite results have followed and incidently other 
problems than those named above have presented themselves during 
the work and in part been solved. During June and July the small 
pelagic eggs of Ctenolabrus and Serranus were used. During July 
the large eggs of Fundulus gave especially favorable material. The 
eggs were in all cases fertilized artificially and the experiments were 
in most cases repeated many times. 
Cleavage. 
Wuirman and H. V. Wınson have figured accurately the segmen- 
tation stages of Ctenolabrus and Serranus respectively. The blastodise, 
circular in outline, elongates at the first cleavage. The elongation is 
in the direction of the nuclear spindle. The second cleavage furrow 
is at right angles to the first and prior to its appearance the cells 
elongate in the direction of the new spindles or at. right angles to the 
first elongation. At one period in the four-cell-state the blastoderm 
is again circular in outline. During the third cleavage the elongation 
of the blastomeres is in the same direction as the first elongation or 
52 * 
