No. 1.] VARIATIONS IN LIMULUS POLYPHEMUS. 79 
and presents a very good case of transverse fission, accom- 

Fig. 8. 
Diagram to illustrate the probable proportional composition of double embryos out of 
old and new parts. 

Fic. 9. 
Diagram to illustrate the relation of old and new parts in the abdomen of separated double embryos. 
panied by median fusion. There is a marked “weakness” 
of the new half of the upper embryo, shown by the absence of 
