324 



EDWARD D. AND RUBY M. CRABB. 



3. Motile embryos show no evidence of attachment to each other. 



4. Each of the 116 young was a normal dextral individual, 

 except for size, when hatched. 



LITERATURE CITED. 



Crabb, Edward D. 



"270 The Fertilization Process in the Snail Lymruza stagnalis appressa Say. 



BIOL. BULL., Vol. 53, No. 2. 

 '276 The Anatomy and Functions of the Reproductive System in the Snail 



Lymncea slagnalis appressa Say. BIOL. BULL., Vol. 53, No. 2. 

 Hall, R. P. 



'25 Twinning in a Mollusc, Serpuloides vermicularia. Science, 61, No. 1591. 



p. 658. 

 MacCurdy, H. M. 



'09 A Double Snail. Rept. Mich. Acad. Sci., Vol. n, p. 119. 

 Newman, Horatio H. 



'23 The Physiology of Twinning. Chicago. 



