298 PROCEEDINGS OF SECTION D- 



The first, fourth and seventh hnes show the normal hfe-history 

 of the biological subspecies coronatiim, trabecula and Ehrenbergii 

 respectively, the youngest forms on the left. The sign = denotes 

 connection by growth and development, principally in length. 

 The vertical lines show the points at which and the intermediate 

 forms through which ascent takes place from one subspecies to 

 another. 



From this chart it will be seen that truncatum, maximum, 

 Archerii, baculoides are not species but merely shapes, which occur 

 and recur at various stages of the development of one Desmid. At 

 three different points we meet with the same trio of shapes closely 

 connected in life and growth : — 1. Baculum, a strongly constricted 

 form, drawn in above the constriction and more or less inflated. 

 2. Baculoides, a severely cylindrical form with decided basal 

 inflation. 3. Ehrenbergii, a cylindrical form with the secondary 

 basal undulations more in evidence. These three are represented 

 again higher up, by var. constrictum mihi, var. Delpontei mihi, and 

 var. Ehrenbergii f. elongata. And again with still larger diameter 

 m var. phcedodermum Schaar. (or var. Georgicum Lagerh.), var. 

 maximum Reinsch., and var. Archerii Delp. 



9.— A CONTRIBUTION TO THE STUDY OF THE PRECIPITINS. 



By Dr. H. G. CHAPMAN. 



The application of the precipitin reaction to the elucidation of the 

 blood relationship of the species of the animal kingdom has shown 

 that the test may be used to determine such relationships as are 

 established by morphological study. 



The use of the test has now been extended to the vegetable 

 kingdom, and the preliminary investigations recorded in this paper 

 show that the test may be employed in the vegetable kingdom to 

 determine the relationship of plant species. The method should 

 be of value, as it is not easy to determine the degree of relationship 

 of different plants by morphological means. 



Experiments on the nature of the reaction are also recorded. 

 The application of the test to the diagnosis of hydatid disease, as 

 carried out by the author in conjunction with Professor Welsh, is 

 also mentioned. 



It has been found that a precipitate or deposit is frequently 

 formed when the serum of a person containing a hydatid cyst is 

 mixed with fluid from a hydatid cyst. Whenever such a deposit 

 is produced a cyst is present in the person. No precipitates or 

 deposits are formed when the serum from a healthy person is mixed 

 with hydatid fluid. The test has been found of much value in some 

 cases in which a diagnosis could not be made by other means. 



