Anatomical structure of Aspidogaster conchicola. 485 



between cuticle and peripheral muscles, or between the different layers 

 of these muscles. It no doubt presents differences of character and 

 relations in different species. It is the layer variously named: Sub- 

 cuticularschicht, Drüsenschicht, klein kernige Zellen, 

 chromatophile Zellen, Matrixzellen, Subcuticular- 

 drüsen, Körnerschicht, Subcuticularzellen, chromato- 

 phile Subcuticularzellen, Ektoparenchym, die peri- 

 pherische Schicht des Körperparenchyms etc. each de- 

 signation probably being understood by its author to include or exclude 

 elements which in another species can or can not be found or is 

 differently interpreted. 



In well stained preparations under a low power it immediately 

 catches the observation as a more deeply colored aggregate of small, 

 nucleated, protoplasmic cells (Fig. 1, 2, 7, 21, 19) between the sub- 

 cuticular muscle-layers and the pale vacant parenchyma. On close 

 observation, however, and with high powers, it is not easy to prove 

 its cellular constitution — presenting, as it does more generally, the 

 appearance of nests of nuclei lying in a common mass of protoplasm, 

 or in a single large cell. The nuclei are large with large nucleoli, 

 and are grouped, two or three layers deep, sometimes in a continuous 

 ring, or often broken into separate bunches which may be connected 

 by a string of single nuclei. The cell protoplasm is present in such 

 a limited quantity and its periphery so delicate that it is only rarely 

 one finds the complete cell distinctly presented to the eye. Along 

 the side walls of the foot the occurrence of nests of large, clear nuclei 

 enclosing spherical nucleoli is characteristic. 



In living animals, under the oil-immersion lens, these cells appear 

 exactly like the cells of the embryo (Urparenchymzellen , Meristem- 

 zellen). Focussing very slowly and carefully from the surface down- 

 wards these primitive parenchyma cells (Fig. 31a) come into view, 

 and, after being acquainted with their structure and distribution in 

 sections, they are here best studied. In the smallest of them there 

 is a scarcely visible layer of hyaline protoplasm uniformely distributed 

 round the nucleus. Larger cells show often a bulging of the proto- 

 plasm to one side from the nucleus, and in still larger I have often 

 observed a lengthening into a point. In methylen-blue preparations, 

 also, some of the subcuticular cells showed a small, narrowing, straight, 

 or curved extension, in form like minute unicellular glands, I have 

 not been able to pursue these processes into ducts, and they do not 

 always point towards the surface. Moreover the cells themselves do 



