484 



NA TURE 



[September 17, 1891 



B. Karyooamy : the union of cells (gametes), cytoplast to 

 cytoplast and nucleus to nucleus, to form a i-nucleate 

 cell, the zygote. The following variations occur : — 



1. IsoGAMY. The union of gametes undistinguish- 



able in size, form, and behaviour ; this may vary 

 as follows : — 



(a) Multiple : between several gametes (up 

 to 6). 



{b) Binary : between a pair of gametes ; 



or, from another point of view— 



{c) Indifferent : between any gametes of 

 the species. 



(^) ExoGAMOUS : between gametes of dis- 

 tinct broods only. 



{e) Endogamous : between gametes of the 

 same brood only. 



2. Anisogamy : the union of two gametes differing 



chiefly in size ; the smaller {micro) gamete is 

 male, the larger {mega-) gamete, female. 



3. Hyperanisogamy : the female gamete, at first 



active, comes to rest before fusion with the male. 



4. Oogamy : the female is never actively motile ; 



the male is termed a spermatozoon, the female an 



From another point of view karyogamy is — 



5. ZooiDiOGAMOUS : one gamete at least is actively 



motile (flagellate, ciliate, or amoeboid). 



6. Siphonogamous : karyogamy is effected by a 



tubular outgrowth from one or both of the 

 gametes. 



II. In apocytial fungi multinucleated masses of protoplasm 

 {gametoids) m&y conjugate to form a zygotoid, by a siphono- 

 gamous process. The union may be isogamous or anisogamous. 



III. Gametes may be classified as follows : — 



A. According to their /^^-wa/i'^w — 



1. EUSCHIST : formed by repeated complete divisions 



from a parent cell, the gametogonium. 



{a) Euthyschist : each nuclear division is 



accompanied by cell division. 

 {b) Bradyschist : the nuclear divisions are 



completed before any cell division takes 



place. 

 {c) IsosCHiST : the brood-cells of a gameto- 

 gonium are all equal and functional. 

 {d) Anisoschist: the brood-cells are unequal, 



some of them being reduced to aborted 



or degraded gametes. 



2. Hemischist : the divisions are limited to the 



nucleus, none occurring in the cytoplasm. 



3. Aposchist : the cell divisions do not occur, but 



a cell directly assumes the behaviour of a 

 gamete. 



4. Symphytic : the gameto-nucleus is formed by the 



fusion of several nuclei. 



B. According to their behaviour, as — 



1. Facultative : retaining the power of develop- 



ment if karyogamy fails to occur. 



2. Obligatory : with no power of independent 



development. 



IV. Paragenesis will include the following modes, usually 

 grouped under the term parthenogenesis, apogamy {pro part"), 

 &c. :— 



A. True Parthenogenesis : the direct development of a 

 facultative gamete without karyogamy. This may 

 occur in the case of — 



(l) Isogametes ; (2) Anisogametes (male and female) ; 

 (3) Oogametes. 



NO. II 42, VOL. 



44] 



B. Simulated Parthenogenesis :— 



1. Cellular : a cell assumes directly the behaviour 



of a zygote. 



2, Apocvtial : a multinucleate mass of protoplasm 



assumes directly the behaviour of a zygotoid. 



C. Metagametal Rejuvenescence : — 



1. Unicellular : a single cell in the neighbourhood 



of the gamete assumes the form and behaviour of 

 the zygote. 



2, Multicellular : a mass of cells in the position 



where gametes should be produced, assumes the 

 character of the young organism formed by the 

 zygote. 



D. Paragamy or Endokaryogamy : vegetative or gametal 



nuclei lying in a continuous mass of cytoplasm fuse to 

 form a zygote nucleus. 



1. Progamic paragamy : the fusing nuclei are the 



normal gametonuclei of the progamous cell (ovum 

 which has formed i -polar body). 



2. Apocytial paragamy : the vegetative nuclei of an 



apocylium fuse to form a zygote nucleus. 



The President of the Section read a paper by himself and 

 Miss Dorothea Pertz, on the artificial production of rhythm in 

 plants. Theapparatus, devised by the Cambridge Scientific Instru- 

 ment Company, was exhibited. The plant is subjected to a series 

 of alternate and opposite influences from light or gravitation, 

 as the case may be. The plant to be experimented with is 

 fixed to a spindle, which, by a clockwork escapement, makes a 

 sudden semi-revolution every half-hour. When the clockwork 

 is stopped, the plant continues to curve with an acquired rhythm, 

 as if the machinery were still in action. This is similar to 

 certain natural rhythms — for instance, to the " sleep " of flowers, 

 which for a short time continue to open and shut although kept 

 constantly in the dark. 



Prof. Green read a paper on the occurrence of diastase in 

 pollen. The starch in the pollen grain serves as nutriment for 

 the- growing pollen tube, and the presence of the ferment 

 converting it into sugar enables it to travel along the growing 

 tube. 



Prof. Vines, in a paper upon diastase in foliage leaves, con- 

 troverts the opinion of Prof. Wortmann, who stated that diastase 

 was either absent from the foliage leaves of plants, or present in 

 such minute quantities that it could be of no physiological im- 

 portance. It is this diastase, and not the protoplasm of the cells, 

 which converts the starch accumulated in the leaves into sugar. 



Canon Tristram exhibited and made remarks upon the smallest 

 known species of parrot, of which the skin measured only two 

 inches in length. 



THE CONGRESS OF HYGIENE. 



VA/'E printed on August 20 (p. 303) an account of some of the 

 work done in the Section of Preventive Medicine in the 

 Congress of Hygiene. The following is the conclusion of our 

 report : — 



Alcoholism. 



Sir Dyce Duckworth, of London, opened a discussion 

 on "The Relation of Alcoholism to Public Health and the 

 methods to be adopted for its Prevention." 



Prof. Harald Westergaard, of Copenhagen, followed with a 

 paper on the same subject. What are the losses of life, he asked, 

 caused to a population by intemperance ? This question can to 

 a certain extent be answered by examining the causes of death, 

 especially delirium tremens and chronic alcoholism. It has been 

 objected that these causes of death supply an unsatisfactory 

 picture of drinking excess, because the wish to spare the feelings 

 of surviving relatives makes returns of such deaths less trust- 

 worthy, and it has therefore been proposed to use other diseases 

 as a measure — such as liver disease (especially cirrhosis of the 

 liver). Yet it is worth while to examine the above-mentioned 

 causes of death. In most countries the statistics of the cause of 

 death do not allow conclusions with regard to alcoholism corre- 

 sponding to those for Denmark and Norway. But, at all 



