June 12, 1908] 



SCIENCE 



917 



have been reported and in some eases com- 

 plete degeneration of ganglion cells has 

 been said to occur. 



In a series of experiments on the ab- 

 dominal ganglia of the crayfish, Cambarus 

 iartonii Gir, ganglion cells have been 

 found to undergo degeneration in twenty 

 to thirty-eight days after the connectives 

 anterior and posterior to the fifth ganglion 

 have been severed. A smaller number of 

 cells were affected in the fourth and the 

 sixth than in the fifth ganglion. The his- 

 tological changes in these ganglion cells are 

 apparently similar and correspond to those 

 described for similar structures in the 

 nerve cells of vertebrated animals. 



Place-modes for the Sacrum and the First 



Hwmal Arch of Necturus: Frank Smith, 



University of Illinois. 



Data on the sacrum and first hffimal arch 

 of 504 specimens of Necturus form the 

 basis for place-modes of these two charac- 

 ters in specimens collected in Lake Erie at 

 Venice, Ohio. 



Of sacra involving two symmetrically 

 placed sacral ribs, eight are modifications 

 of the eighteenth vertebra, 347 of the nine- 

 teenth, 78 of the twentieth and two of the 

 twenty-first. Two specimens have each 

 two pairs of sacral ribs, one pair each on 

 the nineteenth and one on the twentieth 

 vertebra. Fifty-two specimens have two 

 sacral ribs asymmetrically disposed. These 

 involve two of the eighteenth, nineteenth, 

 twentieth and twenty-first vertebra and are 

 found in five of the six possible relations. 

 Twenty-five have the right sacral rib in ad- 

 vance and 27 the left one. Fifteen speci- 

 mens have three sacral ribs which involve 

 two of the eighteenth, nineteenth and 

 twentieth vertebrae and have seven of the 

 eight possible relations. Four have the 

 unpaired rib anterior to the paired ones, 

 and the others have it posterior. 



The first hsemal arch is on the twenty- 



second vertebra in 177 specimens, on the 

 twenty-third in 303 and on the twenty- 

 fourth in 24. In two specimens a half 

 hsemal arch is formed on the twenty-first 

 vertebra. Of thirty sacral ribs borne on 

 the eighteenth vertebra, all but one are 

 associated with a hsemal arch on the twenty- 

 second, and nearly all are in males. The 

 correlation coefficient between the position 

 of the sacrum and that of the first hamal 

 arch is .47 ± .013. 



Three hundred and nine specimens ex- 

 amined for sex include 129 males and 180 

 females. A comparison of the mean posi- 

 tions of the sacral ribs and of the first 

 hffimal arches of the sexes shows clearly 

 that the sexes should be considered sepa- 

 rately in determining place-modes. Vari- 

 ability in both characters is somewhat 

 greater in the males. 



Mean of positions of attachment of sacral 

 ribs in 504 Lake Erie specimens, 19.19 ± 

 .014; in 129 males, 19.126 ±.03; in 180 

 females, 19.28 ± .025. Mean of positions 

 of first hiEmal arch in 504 specimens, 

 22.70 ± .015 ; in 129 males, 22.57 ; in 180 

 females, 22.82. These means are exceeded 

 by the corresponding ones for the 100 

 specimens studied by Bumpus by an 

 amount greater than that involved in the 

 probable errors. 



The Habits and Strtictures of the Larva 

 of Cidex perturians: John B. Smith, 

 Rutgers College. 



The larva of Culex perturbans is unlike 

 that of all other known culieid larvEe in 

 that it does not live in free water or 

 merely on the bottom surface. It works 

 its way into the soft bottom mud a dis- 

 tance of from two to four inches and at- 

 taches itself by its modified anal siphon 

 to the roots of grasses. By means of ser- 

 rated processes it breaks through the outer 

 surface of the roots, attaches itself by 

 means of recurved hooks, and obtains its 



