OF THE INVERTEBRATE ANIMALS. 39 



of " animal ;" we have here no stomach, no internal cavity for 

 the assimilative process, no spontaneous motion ; in short, it is a 

 perfect j)arent-cell of an Alga. The embryo which on the 

 Wsting of this so-called parent-animal begins to pass through 

 its independent vital cycle, exactly resembles Vaiicheria* ; like 

 the latter, when the ciliary motion has continued for two hours, 

 it becomes fixed, and thus attached becomes developed into 

 perfect polypes ; in the first stages of this process it is a true 

 alga, in the latter an animal organism f. We may regard the 

 Alga as an interrupted formation of the polype, as polypes with 

 a simple alternation of generation, whilst Campanularia pos- 

 sesses a double one ! We probably have exactly the same re- 

 lation in the Medusa, Salpce and Ascidi(P, and also as experi- 

 mentally proved in numerous parasites {Ascaris) %, the consider- 

 ation of which here would lead us too far, and which is at once 

 seen when the views we have detailed are compared with the 

 ingenious ideas and excellent observations of Steentrup in the 

 work we have quoted. 



Lastly, these Frustulice — with their vegetable mantle and their 

 vegetable alteration of matter — even with regard to their only 

 animality, the feeble spontaneous motion, are 100 times sur- 

 passed by the embryo of the Algae ! There can be no doubt 

 that they must possess the faculty of converting constituents of 

 the atmosphere into the substance of their organism ; the water 

 of the spring hardly contains traces of organic compounds ; when 

 the air is excluded and it is removed from the influence of light 

 and heat, it remains clear and colourless in sunshine ; without 

 the previous formation of Confervce, without a trace of any 

 other previously-formed formative matter, the few germs of these 

 beings {Frustulice) which have accidentally fallen into it become 

 developed into millions of individuals ; they reduce the carbonic 

 acid of the atmosphere to fats and hydrates of carbon ; they assi- 

 milate the ammonia, or even produce it from the nitrogen of the 

 atmosphere, and combine it with the elements of the fats and 

 hydrocarbons, so as to produce proteine and albuminates ; they 

 separate the oxygen in excess, and man, investigating and reflect- 

 ing from the final product on the " essence " of the process, sees 



* Steentrup, /. c, fig. 51, and in Unger, /. c. 



t Steentrup, /. c, figs. 53 and 57. 



X Auct. id. I. c, p. 50 cl seq. Development of" the Trcmatoda. 



