132 PROTOPLASM 



another, as is well known, by peculiar pillars, which pass 

 vertically through the blood space of the lamella. In an 

 optical transverse section of them these pillars appear as 

 elongated structures which contain numerous nuclei, and 

 consist of beautifully reticulated protoplasm, on the surface 

 of which (towards the blood space) a distinct radiate alveolar 

 layer is formed. The optical longitudinal section of such a 

 pillar shows that it is traversed in the middle by a distinct 

 transverse line of demarcation, and that the pillar consists 

 of beautifully striated protoplasm composed of a meshwork, 

 just as are the ordinary epidermic cells of the gill lamellae. 

 The nuclei lie in the deeper region of the pillar, near the 

 line of demarcation already mentioned. As far, therefore, 

 as I can give an opinion as to the nature of the pillar from 

 a merely cursory investigation, I believe that it is formed 

 by the growth of epithelial cells towards the interior, 

 which, starting from the two surfaces of the gill lamella, 

 meet in its median plane. It is not quite clear to me why 

 I saw no cell boundaries in the optical transverse section of 

 the pillar in spite of its containing numerous nuclei, while 

 the cell boundaries on the surface of the gill lamella can be 

 traced very plainly. A more accurate investigation of sec- 

 tions of the gill lamellae will, however, easily determine their 

 structural relations. 



" The striated nature " of the epithelial cells of the gill 

 lamellae of Asellus was observed by Leydig as far back as 

 1855. He pointed it out again in 1864, and represented the 

 relations somewhat more accurately in 1878 (Asellus, Porcellio, 

 and Gammarus). It seemed to him that the striation depended 

 upon "longitudinal canals or lacunes" traversing the proto- 

 plasm. In surface view the cells appeared as if bored through 

 by very minute, closely approximated holes. E. Hertwig, 1 in 

 1879, mentioned the striated nature in Gammarus. The pillars 

 or trabeculse, briefly described above, which traverse the blood 

 space of the lamella, were also noticed by Leydig in 1878, 

 and he seemed to be of the opinion that they consist of chitin. 

 In the middle of the blood space fat is described as occurring, into 

 which the trabeculse extend, a fact of which I observed nothing 

 whatever. It should be added, however, that he only speaks 



1 Der Organismus der JRadiolarien, Jena, 1879, p. 112. 



