October 31, 19U2.] 



SCIENCE. 



705 



the tubule is situated near the duct as it enters 

 the coil. Models from embryonic glands show 

 that the coiled portion of the sudoriparous 

 glands is developed by a folding- and knuck- 

 ling of the tubule, after the first loop is 

 formed. In the circumanal region are found 

 four quite distinct types of sweat glands : (1) 

 Ordinary sudoriparous glands; (2) the large 

 circumanal glands of Gay; (3) branched 

 tubulo-alveolar glands; (4) a modification of 

 type 3. A large axillary gland reconstructed 

 consists of a single tubule measuring 30 mm. 

 in length, much coiled and folded. In this 

 region are also found branched tubulo-alveolar 

 sweat glands. The glands of Moll are tubulo- 

 alveolar glands, with relatively short but large 

 secreting tubules presenting quite regular 

 alternate enlargements and constrictions, from 

 which arise a relatively small number of short 

 tubules ending in large saccular alveoli. The 

 ceruminous glands are similar to the glands of 

 Moll. Predeeick C. Newcombe, 



Secretary. 



DISCUSSION AND CORRESPONDENCE. 



A QUESTION OF TERMINOLOGY. 



In his review in Torreya of the writer's 

 recent university text-book. Professor L. M. 

 Underwood criticizes severely the use of the 

 termination ' ales ' in class names, the special 

 case cited being ' Anthocerotales,' which was 

 used in conformity with the termination 

 ' ales,' employed in the classes of the Pteri- 

 dophytes, e. g., ' Filicales.' Professor Under- 

 wood says : ' The name [Anthocerotes] is 

 changed to class Anthocerotales, thus improp- 

 erly using a termination reserved for a group 

 of ordinal rank alone.' 



Without referring to other botanists who 

 have also sinned against Professor Under- 

 wood's rule, we should like to ask him to ex- 

 plain certain apparent inconsistencies of his 

 own in this connection. 



In the sixth edition (1900) of his little 

 manual of the fern-allies, Professor Under- 

 wood uses (p. 65) the same names (Filicales, 

 etc.) to indicate the primary divisions of the 

 Pteridophytes that the writer does in the text- 

 book criticized. Professor Underwood, how- 

 ever, calls these orders and not classes as they 



are usually considered to be. Looking for the 

 corresponding class names, we find that Pro- 

 fessor Underwood does not, apparently, recog- 

 nize any classes of Pteridophytes, although he 

 ranks the group as a whole as one of the four 

 subkingdoms of plants. It certainly is not 

 customary among either botanists or zoolo- 

 gists to consider the primary divisions of a 

 subkingdom as of ordinal rank, and it is not 

 quite plain how the employment of the ter- 

 mination ' ales ' is sufficient to convert a rec- 

 ognized class into an order. All of the stand- 

 ard authorities consulted (e. g.. Coulter, Sachs, 

 Scott, Warming, Van Tieghem, Vines) agree 

 in calling the Filicales (or Filicinse) a class; 

 what reason Professor Underwood can give 

 for reducing them to an order is not clear. 

 He can scarcely claim that his ' order ' Fili- 

 cales is of eqiial ranlv with the order Mar- 

 chantiales, for example. 



Moreover, Professor Underwood is not as 

 clear as he might be in distinguishing fami- 

 lies and orders. Thus, on page 63 we find 

 order Equisetacese, order Calamariacese; on 

 page 65, order Eqiiisetales ; on page 126, family 

 Equisetacese. A similar confusion is evident 

 in the discussion of the classification of the 

 other subkingdoms (pp. 56-58). Algse and 

 Fungi are divided into ' classes ' ; Bryophytes 

 into ' groups ' ; Pteridophytes into ' orders ' ! 



Perhaps Professor Underwood, as a pro- 

 fessed systematist, will explain the principles 

 upon which his classification is based. 



Douglas Houghton Campbell. 



Stanford University. 



the expansion of a gas into a vacuum and 



THE kinetic theory OF GASES. 



In number 406 of this journal (for October 

 10) Mr. E. W. Wood calls attention to the 

 fact that the subject of a communication pre- 

 sented by me before the chemical section of 

 the American Association for the Advance- 

 ment of Science at the last meeting and of 

 which communication an abstract* under the 



* The abstract was made without my knowl- 

 edge and, although it is not bad, there are some 

 loose statements in it. The full article will 

 shortly appear in the Journal of Physical Chem- 

 istry. 



