CROSS FERTILIZATION. 177 



may be analyzed by those very differences. It is probably a 

 significant comparison that if an Echinarachnius egg is activated 

 by the sperm of a somewhat distantly related species, development 

 goes through to pluteus formation if the maternal chromosomes are 

 present, but does not go beyond the blastula stage if the maternal 

 chromosomes are absent. The exact meaning of this involves an 

 explanation of the interaction of the various factors concerned at 

 various stages of development in whole eggs and enucleated 

 ones, i.e., the maternal cytoplasm into which was released 

 maternal nuclear substances at maturation; the later effects of 

 maternal genes; and the later effects of genes of another species. 

 It is such an analysis of these factors that this type of experiment 

 is designed to effect, but the failure of the embryos from enucle- 

 ated eggs to develop beyond a blastula prevents an analysis of 

 the problem. Whether or not a gastrula and pluteus can 

 develop from an enucleated egg of one species when activated by 

 the sperm of another species, that is sufficiently distant in re- 

 lationship to have different larval characters, awaits the results 

 of further experiments on various forms. 



LITERATURE CITED. 

 Boveri, T. 



'89 Ein geschlechtlich erzeugter Organismen ohne mutterliche Eigenschaften. 



Situngsb. d. Phys.-med. Ges. Wiirzburg. 

 '95 Ueber die Befruchtungs- und Entwicklungsfahigkeit kernloser Seeigel-eier, 



etc. Arch. f. Ent.-mech., Bd. 2. 



'14 Ueber die Charaktere von Echiniden-Bastardlarven bei verschiedenem 

 Mengenverhaltnis miitterlicher und vaterlicher Substanzen. Verhand. 

 d. Phys.-med. Ges. Wiirzburg., Bd. 43. 



'18 Zwei Fehlerquellen bei Merogonie-versuchen und die Entwicklungsfahigkeit 

 merogonisher und partiel-merogonisher Seeigelbastarde. Arch. f. Ent.- 

 mech., Bd. 44. 

 Fry, H. J. 



'24 Cell Dissection by Hand. Anat. Rec., Vol. 28. 



'25 Asters in Artificial Parthenogenesis. II. Asters in Nucleated and Enucleated 

 Eggs of Echinarachnius parma and the Role of the Chromatin. Jour. 

 Exp. Zool.. Vol. 43- 

 Godlewski, E. 



'06 Untersuchungen iiber die Bastardierung der Echiniden- und, Crinoiden- 



familie. Arch. f. Ent.-mech., Bd. 20. 

 Just, E. E. 



'19 The Fertilization Reaction in Echinarachnius parma. II. The Role of 

 Fertilizin in Straight and Cross Fertilization. BIOL. BULL., Vol. 36. 



