SCIENCE. 



57 



experience, we suggest that it may have been the 

 latter, and we do so on the following ground. 

 In 1873 the Rev. W. H. Dallinger, F. R. M. S., 



Fig. 1. 



undertook, with Dr. J. Drysdale, to make a contin- 

 uous microscopical investigation into the life history 

 of a certain species of Monas. For this purpose 

 they constructed apparatus which prevented the 

 evaporation of the water, and the conditions were 

 made perfect, to keep the specimen in a living state 

 for a considerable time under the microscope. They 

 then commenced to watch the monads in turns con- 

 tinuously, keeping the object in view without a 

 break in observations for many days. During this 

 close study of these monads, Messrs. Dallinger and 

 Drysdale also observed an act so similar to that 

 noticed by Dr. Leidy, that we will produce both 

 statements for comparison. 



Messrs. Dallinger and Drysdale found the modes 

 of re-production with the monads to be equally as 

 varied as that known lo exist with the Amoeba, but 

 there was one method which particularly attracted 

 their attention. 



Two monads at times met and touched their 

 anterior ends, swimming freely together (figure 1 1, 

 their bodies then melted into each other, (figure 

 2i: it then became a single oblong mass, the line 

 of juncture slowly disappearing, when after from six 

 to 24 hours, it became rounded, (figure 3) ; at 

 length the edges gave way, and myriads of minute 

 points poured out, which were watched until they 

 developed into perfect monads. 



In figures Nos. (5, 8, 10, 13, 15, 16, 17, 21;* of our 

 illustrations may be seen in the drawings, from Dr. 

 Leidy's work, of what he observed of the mingling 

 of two Amoeba;; he first speaks of their mutual 

 approach, followed by an "embrace," when the 

 jointed ends of the pseudopods fused together, 

 and one sank deep into the body of the other, and 

 eventually assumed the appearance of a sphere ; 

 further internal breaking up was then noticed, but 

 later observation was not made. This is to be 

 regretted as it seems quite probable that as " the 

 melting into each otlier" was proved in the case of 

 the monads to be a sexual act, that the fusion, 

 when noticed by Dr. Leidy in the Amoeba, may 

 have been of the same character. 



The necessity for the continuous mode of study 



Fig. 3. 



of such forms becomes more apparent every day, 

 especially in the case of the Amoeba, for in the 

 very next paragraph to that just quoted, Dr. Leidy 

 states "in my studies of Amoeba proteus I have 

 not been so fortunate as to trace its history from an 

 early period, nor to discover its modes of reproduc- 

 tion/' 



There are other points to which we would refer, 

 but having already exceeded our limit of space, we 

 can only conclude by extending our thanks to Dr. 

 Leidy for this his latest and most valuable contri- 

 bution to Science, and to those who had the fore- 

 sight and judgment to direct its publication. 



* Figures (5, 8, 10. 13, 15, 16, 17, 21) illustrate the series of changes 

 observed in the swallowing and digestion of an A mieba -verrucosa by an 

 A. proteus. From Bristol Marsh, Pennsylvania, August 27, 1876, 500 

 diameters. Fig. (16). Amceba verrucosa, comparatively quiescent with 

 central contractile vesicle. Figs. (5, 8. 10, 13, 15, 17, 21). Successive 

 changes in shape and relative positioa cf A. proteus during the act of 

 swallowing and digesting the former. Fig. (21). A. proteus approaching 

 the A. verrucosa with anterior short diverging pseudopods. Fig. (8). 

 The A . proteus embracing closely the A . verrucosa by a pair of digitate 

 pseudopods, the points of contact of which being marked by the left hand 

 arrow. Fig. < 1 3 j . The A. verrucosa swallowed and forming a large 

 sphere within the A . proteus. Fig. 1 101. The A. verrucosa, within the 

 latter, has assumed an oval form, and is contained within a vacuole. The 

 central contractile vesicle, which until now had remained persistent, had 

 become less distinct. Fig. 1151. The A. verrucosa has assumed a pyri- 

 form shape within a large elliptical vacuole and its contractile vesicle dis- 

 appeared. Fig. '5). The A . proteus in the act of discharging a diatom 

 while the A . verrucosa has become doubled on itself. Fig. (17). The 

 remains of the A . verrucosa seen as five granular balls within the A . p>o- 

 teus. Later these balls disappeared and their material appeared to be 

 diffused among the granular contents of the A . proteus. 



