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SCIENCE 



[N. S. Vol. XXXIV. No. 881 



of the poison of the gall insect"; and Sir 

 James Paget as late as 1880 said that "the 

 most reasonable, if not the only reasonable 

 theory, is that each insect infects or inoculates 

 the leaf or other structure of the chosen plant 

 with a poison peculiar to itself." In brief, the 

 theory of a stimulus due to a chemical sub- 

 stance injected into the plant by the female at 

 time of egg laying was the accepted view of 

 scientists from the publication of Malphighi's 

 " De Gallis " in 1686 until about thirty years 

 ago. However, from about 1877 to 1882 there 

 appeared a number of important publications 

 by Dr. Hermann Adler and Dr. M. W. Beyer- 

 inck which in a great part disproved the pre- 

 viously almost undisputed theory. From this 

 time the study of cecidology became a grow- 

 ing factor in plant physiology and plant 

 pathology. 



Beyerinck's work indicated that the fluid 

 injected by mother insect was tasteless and 

 odorless and not perceptibly irritating when 

 injected under the skin and that it probably 

 served only as an antiseptic dressing to the 

 wound of the host plant. The work of both 

 authors indicated that there was no cell ac- 

 tivity on the part of the host plant leading to 

 gall formation until the larvas emerged from 

 the egg. Adler, as a result of a careful study 

 of the galls of Neuroterus Iwviusculus and 

 Biorhiza aptera, states that immediately fol- 

 lowing the emerging of the larvas from the egg 

 that there is a rapid division of the cells of 

 the host plant due to the attacks of the larvae. 

 He was inclined to believe this due to the 

 influence of salivary excretions. However, 

 Adler also made a study of the Galls of Nema- 

 tus vallisnierii on Salix amygdalina, which is 

 produced immediately following oviposition 

 and is fully developed before the hatching of 

 the larvse. This is probably the only well 

 authenticated case of gall formation previous 

 to the hatching of the larvse and is undoubt- 

 edly the exception rather than the rule for gall 

 builders. 



It is well known that the gaU makers be- 

 longing to the Cecidomyidse, Aphididse and 

 Acarina do not puncture the plant tissues with 



the ovipositors and that the young insects are, 

 strictly speaking, never within the tissues of 

 the host plant but are surrounded by plant 

 growths due to an irritation by their own 

 mouth parts. 



At the present time there is no proof, except 

 in the case of Nematus vallisnierii that the 

 gall is due to a secretion from the mother 

 insect. Whether due to a chemical or a 

 mechanical irritation of the young insect are 

 questions with as much circumstantial evi- 

 dence for the one as for the other. 



It may be added that the studies of the past 

 few years on cecidia due to bacteria, myxo- 

 myeetes, fungi and nematodes indicate certain 

 striking resemblances to the zoo-eecidia and 

 we have reason to believe that further re- 

 searches into the anatomy and physiology of 

 these various groups of hypertrophied struc- 

 tures will lead to valuable contributions to our 

 knowledge of cecidology. 



Mel. T. Cook 



Agricultural Experiment Station, 

 Newark, Delaware 



the air-bladder of the clupeoid fishes 

 In a recent letter (Science, October 13) 

 Dr. E. C. Starks has suggested that the pos- 

 terior opening of the air-bladder in Clupea 

 harengus needs further investigation. This 

 opening was originally described by Weber in 

 1820, was rediscovered by Bennett in 1880, 

 and was again described by Dr. Eidewood in 

 1892 in a paper entitled " The Air-bladder and 

 Ear of British Clupeoid Eishes " (Journ. 

 Anat. Phys., XXVI., pp. 26^2). Dr. Ride- 

 wood devoted a special section to the posterior 

 opening to the exterior ; he showed that it was 

 present not only in Clupea harengus, but in 

 G. pilchardus, G. sprattus, G. alosa and En- 

 graulis encrasicholus. In Glupea finta, how- 

 ever, he found that the air-bladder tapered to 

 a point posteriorly and did not open to the 

 exterior. 



C. Tate Eegan 

 British Museum (Natural History), 

 London, S. W., 

 October 30 



