No. 550] NOTES AND LITERATURE 



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for "lateral bands of the lemmatochord. " This same figure 

 shows a "median portion of the lemmatochord" distinctly and' 

 widely separated from the lateral portions. The inference is 

 that these lateral and median structures unite somewhere; but 

 no direct statement to this effect is given, at least in the section 

 on the middle cord of Limulus. 



Again, Fig. 225, p. 328, presents five cross sections of the 

 nerve cord of an adult scorpion. Section 5 is said to show the 

 "merochord." Neither in the description of this figure nor in 

 the text do we find a direct letter reference to the merochord. 

 A structure labeled m appears in the figure, but on turning to 

 the explanation of lettering "m" we find may stand for- 

 "mouth" or "muscle." But it is unfair to criticize illustra- 

 tions and their letterings and labels alone. They must be taken 

 in connection with the text. By reading a subsection headed 

 "The Bothroidal Cord or Lemmatochord" we find that the 

 merochord in section 5 of Fig. 225 is marked l.ch., which stands 

 for lemmatochord. A sufficiently careful reading of the text 

 clears up the merely expositive difficulties contained in the figure : 

 The merochord is the lemmatochord of the "posterior thoracic 

 neuromeres," p. 328. This interpretation is compelled when 

 Fig. 5 is taken in connection with the text statement indicated. 

 But then the difficulty becomes substantial and not merely ex- 

 positive, for on page 328 we read: "In the scorpion, the median 

 nerve itself is hardly recognizable. . . . The neurilemmas of the 

 median and lateral cords form the bothroidal cord of the ab- 

 domen and the merochord of the posterior thoracic neuromeres." 

 But we have seen above that according to section 5 of Fig. 225 

 the merochord is a particular part of the lemmatochord. Hence 

 this part at least of the lemmatochord is formed from the neuro- 

 lemmas of the median and lateral cords. Under the topic "De- 

 velopment of the Lemmatochord" we read "The lemmatochord 

 arises, in part, as an axial cord of cells extending forward from 

 the primitive streak"; and nothing under this heading or else- 

 where so far as I have been able to find, harmonizes this state- 

 ment with the indirect assertion above pointed out that the- 

 lemmatochord is formed from the neurilemmas of the median 

 and lateral cords. The nearest approach to such harmonization 

 is the statement, p. 330, that at the time of hatching, the lem- 

 matochord at certain places "remains permanently attached to 

 the neurilemma of the middle cord." As- one of the many stu-- 



