76 LILLIE. [Vol. X. 



Appendix. 



The appendix includes the results of some of the most 

 important works on the cell lineage of worms and molluscs 

 reduced to tabular form. It is inserted as a possible con- 

 venience to other workers in the same field. The system of 

 naming the cells is the one employed in this paper, with the 

 original designations in brackets. The necessary remarks 

 have been made as brief as possible. 



Kofoid has already published a criticism of Blochmann's work 

 (Table I) based on the internal evidence, and I can only concur in 

 his judgment. Referring for the evidence to Kofoid's prelimi- 

 nary paper (No. 49'^), I will merely note the probable errors. 

 The trochoblasts are, according to Blochmann's derivation, 

 ^2.1.2.1 and ^2.'.2.i ^^ table) ; but there is almost no doubt that 

 the cells in question are a> and c^. The inner cell of the cross 

 would be «*•'•» to (P--^-^ according to Blochmann's derivation, 

 whereas there is but little doubt that it is «'-^ to d^'', thus a 

 member of the first group of micromeres. It is, however, 

 rather unsatisfactory to criticise a work from internal evidence 

 alone ; but until such manifest discrepancies between text and 

 plates, as occur in Blochmann's work, are explained, it is impos- 

 sible to place great reliance on them, 



Rabl (Table II) has evidently been in error in the orien- 

 tation of the embryos. If we are to accept his figures, 

 the first generation of micromeres is formed leiotropically. 

 The second generation is formed in the same way. It rotates 

 the first generation of micromeres still further to the left. 

 The rotation goes on, according to the figures, until finally «' 

 is above C and c^ above A. That is to say, what was on the 

 right side is now on the left side of the embryo and vice versa; 

 similarly what was anterior (of the first generation of micro- 

 meres) has become posterior and vice versa. It seems difficult 

 to accept this as being really true. The first error, it seems 

 to me, was probably in his assigning the members of the first 

 generation of micromeres to wrong macromeres as parent cells. 

 Thus E should not have been assigned to EJ, but to ME, etc., 

 which would make the direction of its formation dexiotropic. 



