52 



nianii has described a Gregarina from Gammarus putaneus ; 

 and Kolliker made us acquainted \^'\\\\ the Gregarina Balani 

 which he had observed in Ba/anus pusillus. 



I have the honour, on the present occasion, to present a 

 description of a new species of Gregarina which lives in the 

 intestine of the Lobster. It is chictly remarkable for its great 

 size, and it is on this account that I propose to call it Gre- 

 garina gigantea. Thanks to its size I have been able to 

 ascertain some new facts relative to the organisation of these 

 animals, and some of these observations are not without im- 

 portance in relation to the theory of the cell. I have found 

 besides some facts relative to the development of this Gre- 

 garina which will contribute to complete our knowledge 

 relative to the history of the development of these singidar 

 parasites. 



Description. — The Gregarina of the Lobster has a very much 

 elongated form, which gives it a superficial resemblance to a 

 Kematode. The largest individuals I have had under my 

 observation did not measure less than sixteen millimetres 

 in length, Avith a breadth of '15 of a millimetre. The body 

 presents nearly the same breadth throughout, excepting in 

 its posterior part, where it diminishes progressively. The 

 anterior extremity, on the contrary, rounded in front, is 

 slightly swollen out into a globular form : the Gregarina 

 gigantea belongs to the division which M. Kolliker charac- 

 terised by these words — " Eingeschniirte Gregarinen, mit 

 einem cinfachen abgerundcten \'orderende." 



The structure of these Gregarina? is very simple ; I con- 

 sider them with M. Kolliker as monocellular animals; in 

 them are found all the constituent elements of a cell, and it 

 is impossible to find in their structure a fact Avhich is of such 

 a nature as to throw doubt on their monocellular constitution. 

 Here we have, therefore, an animal cell which can reach the 

 length of sixteen millimetres. I believe that, as far as simple 

 cells are concerned, there are only the eggs of birds and of 

 some other animals which surpass in their dimensions those of 

 the cell which concerns us here. And there is this difference 

 between the egg of these animals and our monocellular or- 

 ganism, that in the egg of the bird one has to distinguish a 

 living, active part (the cicatricula), and an inert passive part 

 (the yellow), which forms almost the whole of the c^^. For 

 this inert part of the egg-cell does not form an integral part 

 of the cell. It is found within the cellular membrane truly 

 (vitelline membrane), but the only living part of the cell is 

 the cicatricula; it alone divides and gives rise to the cells of 

 the embryo. In the Gregarina, on the contrary, all the parts 



