490 THE AMERICAN NATURALIST. [VoL. XXXIV. 
acceptance. The presence of antherozoid in gymnosperms 
was demonstrated. 
In the field of fertilization studies, the opinion that the cen- 
trosome of the fertilized egg comes exclusively from the sperm 
was still dominant, despite the contradiction of Myzostoma ; 
but the continuity of the centrosome was still debated. 
Parthenogenesis. — A difference in structure between the 
parthenogenetic and the sexual egg of Rotifera was affirmed, 
and it was asserted that while in the female parthenogenetic 
egg of Rotifera only one polar globule is formed, two are per- 
manently extruded when the parthenogenetic egg is destined to 
produce a male. 
Asexual Reproduction.—It has long been recognized that 
the organs of an individual produced by budding or fission 
develop differently from those of an egg-individual. This dif- 
ference can be referred to the dissimilarity of external condi- 
tions in the twocases. Thus von Bock showed that in dividing 
Cheetogaster the mouth of the new zoóid arises from two lateral 
invaginations instead of one ventral one, because the ventral 
position of the nerve cord interferes with a median invagina- 
tion. Heschler showed that the regenerative capacity of the 
earthworm is greatest in the region where autotomy normally 
occurs. Bordage extended our knowledge of autotomy in 
Orthoptera. 
Ontogenesis. — Echoes of the preformation-epigenesis con- 
troversy continued. Fischel, working with isolated blastomeres 
of ctenophores (Beroé), concludes that they afford a good exam- 
ple of preformation. Attempts to influence development by 
external means were richly rewarded. Hertwig transformed the 
holoblastic egg of the frog into a meroblastic one by condens- 
ing the yolk by means of a centrifugal machine. It was shown 
that salamander eggs reared in the dark became in certain par- 
ticulars abnormal, and that electric rays accelerate the respira- 
tion of the eggs of the silkworm and hasten their hatching. 
Teratogenesis. — Especially important is the experiment of 
Tornier, by which doubly and triply tailed lizards may be pro- 
duced by making a triangular incision through the muscles and 
into the vertebra. Also if a limb is transsected and a thread 
