DALLINGER AND DKYSDALE, 1873-1875. E. DE FROMENTEL, 1876. 29 



interest and value attached to the results achieved by these joint workers 

 is accomplished through their having struck upon and most successfully 

 followed up an entirely new channel of discovery. Employing the highest 

 and most perfectly constructed modern powers of the compound microscope, 

 and concentrating upon their task an amount of energy and patience 

 scarcely before equalled, Messrs. Dallinger and Drysdale directed their 

 attention to unravelling the mystery so long associated with the incon- 

 ceivably rapid production of low flagellate organisms or monads in organic 

 infusions, and more especially such as are so abundantly produced in fish 

 macerations. Taking turn by turn at the microscope, and patiently watch- 

 ing the same forms from hour to hour and day to day, the entire life-history 

 of numerous species of these most minute organisms was now revealed for 

 the first time. Not only was it found that these animalcules increased to 

 an indefinite extent by the familiar phenomena of longitudinal and trans- 

 verse fission, but also that under certain conditions two or even more 

 individuals of the same species would become intimately united, the result 

 of this fusion or coalescence being the formation of encystments, whose 

 contents broke up into a greater or less number of spore-like bodies, which 

 speedily developed into the parent type. In some cases these reproductive 

 spores were so excessively minute as to defy individual detection under 

 a magnifying power of no less than 15,000 linear, their presence being in- 

 dicated only by their presenting as they escaped en masse from the investing 

 envelope the aspect of a fluid possessing a slightly higher refractive index 

 than the surrounding water. The power to withstand great vicissitudes of 

 temperature — in some cases even up to and beyond boiling point, and pari 

 passu the practical indestructibility of these monad spores — was also proved 

 by these investigators ; the facts elicited as a whole, affording some of the 

 most important evidence yet educed towards the solution of the much- 

 vexed question of spontaneous generation, and in demonstration of the 

 dominance of the inexorable law of " like begetting like " among even these 

 most minute and humble members of the organic world. The special 

 bearing of Messrs. Dallinger and Drysdale's evidence upon these highly 

 interesting points receives extensive notice in a future chapter. 



Among the more recent literary productions bearing upon the subject 

 of the Infusoria, brief allusion must be here made to the ' Etudes sur les 

 Microzoaires ou Infusoires proprement dits,' published by E. de Fromentel 

 in the year 1876. The expectations raised by a first glance at this 

 portly volume and its thirty quarto plates receive a somewhat severe 

 shock on proceeding to a more intimate acquaintance. This writer is 

 apparently entirely ignorant of the work achieved in the same field by 

 Stein, Engelmann, and other modern German investigators, their names not 

 being so much as mentioned throughout the whole course of his treatise. 

 With scarcely an exception, his entire series of diagnoses of the innumerable 

 forms, new and old, are so vague and indefinite as to be scarcely in advance 

 of the necessarily incomplete ones given last century by O. F. Muller, 



