370 



NATURE 



[December ii. 1919 



Genus I. — Entam(i:ba, Cassajjraiidi and Barba- 

 gallo, 1895 ("^'^ Endamoeba, Leidy, 1879). 



Species i. ¥.. colt, Grassi ; 2. E. histolytica, 

 Schaudinn ; 3. E. gingivalis, Gros. 

 Genus II. — Endolimax, Kuenen and Swellen- 

 grebel, 1917. 



Species 4. E. nana, Wenyon and O'Connor. 



Genus III. — IodamQ'BA, nov. gen. 

 Species 5. 1. Biitschlii, Frovvazek. 



Genus IV. — Dientamckba, Jepps and Dobell, 

 1918. 



Species 6. D. fragilis, Jepps and Dobell. 



Of these only Entamoeba histolytica is proved 

 experimentally to be pathogenic ; it causes dysen- 

 tery and liver abscess. None of the' other five are 

 pathogenic. E. coli is proved experimentally to 

 be harmless. It is held by Prof. Dobell, in agree- 

 ment with recent investigators, such as Goodrich 

 and Moseley, that E. gingivalis , common on the 

 human gums, is innocuous and not a cause of 

 pyorrhoea. He cites their observation of the oc- 

 currence of E. gingivalis in pus from the mouths 

 of dogs and cats. Endolimax nana is a small but 

 well-marked innocuous species common in the 

 human bowel. lodamoeba Biitschlii is a small 

 and uncommon species which produces in its cysts 

 a mass of glycogen, which gives the mahogany 

 stain when treated with iodine. Dientninoeha 

 fragilis is a very small form studied only in seven 

 cases. It is typically "bi-nucleate." 



Entamoeba coli is as large as E. histolytica, and 

 the two have been persistently mistaken for one 

 another and confused in name. Even when oc- 

 curring together they have not been distinguished. 

 Hence endless misapprehension and trouble have 

 arisen as to which "Ama;ba" it is that is harm- 

 less and which that causes dysentery. Losch, 

 in 1875, gave the name Amoeba coli to what is 

 now by common consent called Eiitanioeba histo- 

 lytica. Grassi, in 1879, described as the Amoeba 

 coli of Losch, not what Losch had so called, but 

 the harmless form which to-day passes under that 

 name. Schaudinn (1903) described what Losch 

 had named .Amoeba coli under the name Amoeba 

 histolytica. Schaudinn ought to have recognised 

 what he described as being Losch 's A. coli, but he 

 jailed to do so. Hence E. histolytica is to-day 

 the name in use for the dysentery-causing species, 

 and E. coli is that applied (contrary to the original 

 use of the name) to the harmless species. Prof. 

 Dobell declines (and we think rightly) to reverse 

 or interchange the two names again, as such a 

 course would cause "endless confusion." The 

 mere citation of this one example of the 

 misunderstandings of former authorities will 

 serve to suggest to the reader how great are the 

 difficulties in regard to nomenclature and identifi- 

 cation with which Prof. Dobell has successfullv 

 contended. All future workers in this line must 

 be grateful to him for his laborious and judicious 

 treatment of these questions, as well as for his 

 new and accurate observations. 



E. Ray Lankester. 

 NO. 2615, VOL. 104] 



ASTRONOMICAL LECTURES AND ESSAYS. 

 (i) The Adolfo Stahl Lectures in Astronomy. 

 Delivered in San Francisco, California, in 

 1916-17 and 1917-18, under the Auspices of the 

 Astronomical Society of the Pacific. Pp. xiv-l- 

 257 + liv plates. (San Francisco: D. S. 

 Richardson, 128 Lick Building, 35 Montgomery 

 Street, 1919.) Price 2.75 dollars. 

 (2) Planetary Rotation Periods and Group Ratios. 

 By F. A. Black. Pp. xii+115. (Edinburgh 

 and London : Gall and Inglis, n.d.) Price 

 35. 6d. 

 (i) ^PHE Astronomical Society of the Pacific if 

 ■*■ in several respects an interesting and 

 fortunate body. As Dr. Aitken recalls in one of 

 these lectures, it had its origin in the co-operation 

 of amateur and professional observers of the 

 eclipse of 1889, which crossed California and was 

 the object of an expedition, the first of a splen- 

 didly organised series, from the Lick Observatory, 

 then only recently established. The society is 

 essentially an amateur association enjoying the 

 cordial support of professional astronomers, and 

 this means much, for in its province — a thousand 

 miles !ong — is to be found the most notable part 

 of the instrumental equipment of astronomy in the 

 world, including the three largest reflectors, with 

 an average aperture of nearly 80 in. It bestows 

 the Bruce medal on conditions which make the 

 award the seal of the highest professional 

 approval on the work of the recipient. It grants 

 the Donohoe medal to the discoverer of every 

 unexpected comet. Its "Publications," without 

 having the severity of a conventional learned 

 journal, contain notes on results of the most 

 recent work, and often give an intimate account 

 of observatory life in circumstances of peculiar 

 interest, especially welcome to those who have had 

 personal experience of it. 



It was quite in accordance with the aims and 

 spirit of the society that an organised course of 

 six popular lectures should be given in San Fran- 

 cisco by members of the Lick Observatory staff 

 in the winter of 1916-17, and equally fitting, but 

 no less welcome, that a generous benefactor 

 should be found in Mr. Adolfo Stahl to defray 

 the expenses ; for the readiness of Californian 

 citizens to help worthy astronomical projects of 

 all kinds with financial support is unequalled else- 

 where. And Mr. Stahl's liberality did not stop 

 there ; for when the success of the first course 

 suggested a second series in the following winter, 

 this time with the help of the Mount Wilson and 

 the Berkeley staffs, Mr. Stahl again lent the 

 same aid, and when it was very properly felt that 

 the lectures, which had been printed in the 

 "Publications," deserved to be published in col- 

 lected book form, he undertook once more to 

 guarantee the cost. The result is this handsome 

 volume, beautifully illustrated and contaming a 

 dozen lectures, popular in the sense of being 

 simply stated and dealing for the most part with 

 modern aspects of astronomy, by competent 

 authors. 



