112 H. H. NEWMAN. 



pect the larvae to exhibit the various types of developmental de- 

 fects that are commonly seen in inhibited individuals. 



8. In none of the numerous experiments did parthenogenetic 

 'eggs give rise to even approximately normal bipennariae. The 

 most successful larvae were certain double monsters that will be 

 discussed later. 



9. The average viability of parthenogenetic larvae varies greatly 

 in different sets. As a rule viability was lowest in those sets in 

 which the smallest percentage of larvae occurred and highest in 

 those in which the largest percentage of larvae occurred. 



10. Individual viability varies greatly within a given set of 

 e ggs. Quite frequently eggs die and disintegrate during the first 

 or subsequent cleavages, while it was not uncommon for a few 

 larvae in each of the best sets to live for from four to seven days. 



11. Cleavage in parthenogenetic eggs is sometimes very normal 

 in appearance, but in every set the majority of cleavage stages 

 are irregular (Figs. 1-6). Sometimes blastomeres of the two 

 cell stage separate, and form half-sized blastulae, seldom going 

 further. In other cases one or more blastomeres cease cleavage 

 while the rest go on and form a covering of small cells about a 

 large central cell. Numerous other cleavage anomalies occur 

 which need not be detailed here. 



DISCUSSION. 

 Loeb's Observations of Spontaneous Parthenogenesis in Asterina. 



Doubtless the reader recalls the work of Loeb (1905) on 

 "Artificial membrane formation and chemical fertilization in a 

 starfish (Asterina)." In this paper the author describes various 

 methods employed first, for inducing membrane formation and 

 second, for inducing cleavage and subsequent development in the 

 same species of starfish which forms the material of the present 

 investigation. Loeb recognizes the occurrence of spontaneous 

 parthenogenesis in Asterma as is shown by the following quota- 

 tions : " The eggs of the starfish show a slight tendency to develop 

 spontaneously without any external influence." " If the eggs of 

 Asterma are allowed to mature in sea water and are left to them- 

 selves, sometimes none, sometimes a fraction of a per cent., some~ 



