DR. THEODOR NEUMANN. 229 



hermaphroditic, which is produced after the settling 

 down of the larva, and males which remain more or less 

 in the larva state and do not become sessile. Both kinds 

 are, of course, very differently formed; the species is, to 

 use the scientific term, dimorphous, because besides the 

 real animals which have sex we have very small comple- 

 mentary or dwarfish males. 



There is no more doubt now that all parasites are 

 differentiated concerning their sex at some time of 

 their life, and produce fructified eggs from which a new 

 generation is developed. This sounds very simple now, 

 but it required a long time, and enormous difficulties 

 had to be overcome before this fact was recognized and 

 fully established. 



Those eggs seem indeed to be treated rather carelessly, 

 when we compare their way of being brought forth with 

 that of free-living animals. Most of the latter take at 

 least some care of their brood; they deposit them at some 

 place where tuey are protected from outside dangers, 

 and where the embryos coming out of the eggs find at 

 once suitable food and shelter. What a difference from 

 the parasites! They can scarcely ever look out for the 

 welfare of their offspring. They are forced to lay their 

 eggs just there where they are without being able to do 

 the least for their good; they must leave all the follow- 

 ing stages of development to chance. One might think 

 that the continued existence of the young larvae is by 

 no means doubtful, as they are born in a place where the 

 parents have all the conditions of life fulfilled to the best 

 advantage, so that nothing would be left for the young 

 but to grow up beside their parents. This is. however, 

 an impossibility, for the accumulation of parasites in the 

 same host in such a way would lead within a short time 

 to destruction of health and life of the host and would, 

 in consequence, also endanger the existence of the para- 

 sites themselves. Bearing in mind this fact, we are 



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