Miscellaneous. 163 



the water, a single dead fly may become a focus of infection for a 

 great number of aquatic animals (fishes, newts, &c.). The whole 

 surface of the tadpole above mentioned was covered with Sapro- 

 legnia, so that death must have been produced by the suppression of 

 the action of the skin. The second larva, placed in a separate vessel 

 before the introduction of the fly, remained quite intact. — Seance de 

 la Soc. Vaudoise des Sci. Nat. July 6, 1887 ; Bibl. Univ. November 

 15, 1887, p. 492. 



On the Significance of Sexual lieproduction. 

 By Dr. B. Hatschek, 



Dr. Hatschek recently lectured upon this subject before the 

 meeting of German surgeons in Prague. 



In the first place he indicated that the most important and pro- 

 bably original of vital phenomena was assimilation. By the process 

 of assimilation new living particles (that is to say particles which 

 in their turn possess the faculty of assimilation) are produced. 

 Assimilation is, as Hatschek afiirms, the sole Icnoivn mode of produc- 

 tion of fresh living substance. We see in the Amoebae and other 

 unicellular organisms that the parent-creature divides into two 

 daughter-organisms. In the more complex multicellular organisms 

 reproductive bodies in the form of germs and buds are produced ; 

 these are developed, and grow into new individuals of the same 

 kind. In the latter instance, however, the formation of such germs 

 is reduced to a process of division of the same kind as occurs in the 

 unicellular organisms, only that in those cases where we have to do 

 with production of ova, spermatozoa, and buds the portions divided 

 off are very unequal in size. This difference, however, is due to no 

 principial distinction. 



Besides division, however, the contrary phenomenon occurs in 

 unicellular organisms, namely the fusion of two originally separate 

 indiviiduals into a single one. This is the so-called " conjugation," 

 which is very widely diffused among the Monoplastida. In the 

 multicellular organisms it is the portions characterized as reproduc- 

 tive bodies that become fused together, therefore the individualities 

 in their simplest state. The conjugation of the unicellular organisms 

 represents the process of fecundation, but not the copulation of the 

 midticdlu lar forms. 



Tlie intermixture of the individualities is most generally diffused 

 throughout the organic world ; and although among multicellular 

 animals we frequently meet with asexual modes of reproduction 

 (siich as gemmation, division with regeneration, and parthenogene- 

 sis), we find this always only along with sexual reproduction, i. e. 

 alternating therewith. 



When we find any process generally occurring in organisms the 

 question of its significance involuntarily forces itself upon us. We 

 ask directly. What does this arrangement do for the organism, what 

 purpose has it for it? After citing and criticizing the views of 

 Biitschli, Hensen, van Beneden, and Weismann, Hatschek expresses 

 his own theoretical opinion, namely that hi sexual reproduction we 

 must recognize a remedy against the action of injurious variability. 



