EGGS OF ASTERINA (PATIRIA) MINIATA. 1 17 



and tripolar, etc., usually undergo gastrulation in two or more 

 places (Figs. 9, 10, n) and produce double and triple monsters, 

 etc. The most nearly normal forms are decidedly abnormal 

 early bipennaria larvae in which the anterior parts are relatively 

 inhibited. Such a form is shown in Fig. 12, in which the mouth 

 never breaks through, oesophogus is not clearly differentiated, 

 but stomach and intestine are well devevloped. Since I have in 

 preparation a detailed paper on twinning in Asterina, in which I 

 intend to discuss the physiology of twinning in general, I shall not 

 enter further into an account of ' the various types of inhibited 

 larvae that result from spontaneous parthenogenesis, for the same 

 types result from several other kinds of inhibiting factors. In 

 closing I merely wish to emphasize this one point : that the results 

 of spontaneous parthenogenesis are those usually found to accom- 

 pany early grozvth retardation. For a summary of this paper the 

 reader is referred to the eleven points referred to on pages 110- 

 112 and to the italicized clauses in the general discussion. 



I am greatly indebted to the Hopkins Marine Station of Le- 

 land Stanford University, and to its director, Dr. Walter K. 

 Fisher, for the excellent facilities for research that I enjoyed 

 while at Pacific Grove. 



LITERATURE. 

 Loeb, J. 



'05 Artificial Membrane Formation and Chemical Fertilization in a Star- 

 fish (Asterina) Univ. of Calif. Pub., Physiol., Vol. 2, No. 16. 

 '13 Artificial Parthenogenesis and Fertilization. Univ. of Chicago Press. 



