28 A. J. GOLDFARB. 



gastrulse fused so that their axes are about 135 degrees apart. 

 Fig- 37 is a free-hand drawing of this pair. These gastrulse 

 developed into two fused larvae whose axes had rotated from 735 

 to about 170 degrees (Fig. 38). In this pair of larvae it is inter- 

 esting to note that one half of one member has been completely 

 suppressed. 



In the following pair of gastrulae the AXES ROTATED IN THE 



OPPOSITE DIRECTION, AND BECAME SECONDARILY PARALLEL, hav- 

 ing shifted from about 70 degrees to o degrees. The gastrulae 

 were nearly equal in size and their axes diverged about 70 

 degrees (Fig. 39). During the next twenty-four hours no ma- 

 terial change occurred either in size or differentiation of parts, 



BUT THE GUTS HAD BECOME PARALLEL (Fig. 40), and ALTHOUGH 

 THESE GASTRUL.E WERE NOW PARALLEL THEY DID NOT FUSE 



INTO A "SINGLE" LARVA as required by Boveri's hypothesis. 

 It might be urged that while the axes were parallel the two 

 gastrulae were not necessarily blastomerically symmetrical. In- 

 asmuch as I failed to observe the skeletal spicules which would 

 have established the planes of each of the members, I can offer 

 no opinion, in this example. 



In another example a completely differentiated gastrula was 

 fused to one just beginning to differentiate its gut (Fig. 41). 

 This pair is like the one shown in Figs. 33 and 34. Two days 

 later the pair developed into two fused larvae in which the axes 

 had changed from about 100 degrees to 40 degrees (Fig. 42). 

 This pair is also interesting because one individual developed 

 into a perfect larva, while the other developed into a perfect 

 half larva, the two having a common foregut. 



Still more interesting is the pair of gastrulae shown in fore- 

 shortened view in Fig. 43. The axes are about 180 degrees apart, 

 nevertheless during the next seven hours THE AXES HAD SHIFTED 



FROM ABOUT l8o DEGREES TO O DEGREES (Fig. 44). Unlike the 



pair shown in Fig. 40, these gastrulce tended to approach a sym- 

 metrical position, yet in spite of this, developed into two larvce, 

 one of which was quite irregular (Fig. 45). Much to my surprise 

 the axes continued to rotate during late differentiation, but the 

 skeleton and the gut rotated unequally, for the skeleton shifted 

 from o to about 80 degrees and the gut only to about 45 degrees. 



