1908] Davis. — Life-history of DolicJioglossus. 211 



due to the action of reagents. Since, however, the middle meso- 

 blastic tracts in Tornaria are said to be arehenterie diverticula 

 (Spengel, etc.), it seems more likely that the rarity of their 

 occurrence is due to the shortness of the time for which they are 

 present. ' ' 



Of the connection between the posterior body cavities and the 

 archenteron he is more certain. He says (p. 221) : "These 

 mesolilastic pouches open by large foramina into the lumen of 

 the gut." No such large foramina exist in any stage that I have 

 studied in D. pusillus. Although Spengel '77, several years be- 

 fore Bateson's paper, held that the middle mesoblastic tracts in 

 Tornaria are "arehenterie diverticula," he later modified this 

 view, for he says (Spengel '94, p. 431) : "dass die beiden Co- 

 lome jeder Seite aus einer gemeinschaftlichen Anlage hervorge- 

 hen, die spiiter in zwei Theile zerfallt." 



I cannot but think that Bateson failed to notice the connecting 

 links between the mesoderm of the anterior body cavities and 

 that of the other cavities, for his observations of the early back- 

 ward growth of the mesoderm, as well as of the cavities after 

 being formed, agree with mine. Indeed, his fig. 36 shows a com- 

 munication, or at least a close connection, between the middle 

 and posterior body cavities just as I have shown in my fig. 28. 

 The only essential difi'erence between his figure and mine will be 

 seen to be in the definite line which he has draM'n separating the 

 anterior from the middle body cavity. Such a separation does 

 not occur in my sections of the same stage. 



Furthermore the arehenterie walls in the region of the middle 

 and posterior cavities at no time show any evidences of out- 

 pocketing. If these cavities were outgrowths of the arehenterie 

 wall one would expect to find evidences of this growth in the 

 disposition of the cells of these regions. In the early stages of 

 the anterior cavity the cells of the portion of the archenteron 

 giving rise to it are irregular both as to shape and arrangement. 

 The same condition is observed at the blastopore at the time of 

 its closure. But no such irregularity is ever noticed in the arch- 

 entei-ic walls, where according to Bateson the middle and pos- 

 terior outgrowths occur. 



^^lorgan '94 does not accept Bateson's account of the origin 



