316 D. H. TENNENT. 



If the theory of the individuality of the chromosomes is cor- 

 rect and the interpretation of synapsis well founded, experi- 

 ments in hybridization with favorable forms ought to prove the 

 truth of such an explanation. The starfish, owing to our inability 

 to raise adults from the egg and to the extremely small size of its 

 chromosomes, does not seem promising for such an investigation. 



Summary. 

 i. The reduced number of chromosomes in the male germ 

 cells of Asterias vulgaris is 9. 



2. Fertilized starfish eggs contain as a somatic number 18 and 

 36 chromosomes, the difference possibly to be correlated with 

 Asterias vulgaris and Asterias forbesii. 



3. Eggs caused to develop parthenogenetically show one half 

 the somatic number of chromosomes. 



4. No conjugation of individual chromosomes takes place in 

 fertilized eggs immediately before the first segmentation. 



5. A possibly hybrid form contains 27 chromosomes. 

 Bryn Mawr College, 



July, 1907. 



All of the figures are from camera drawings made with aid of 

 Zeiss No. 12 compensating ocular and 2 mm. apochromatic ob- 

 jective. Some of the sketches were subsequently doubled in 

 diameter by means of a drawing camera. These have been re- 

 duced one half in reproduction. The others are reproduced as 

 drawn. 



