tEÜCOPSACÜS ORTHODOCUS. 43 



diameter. It shows a moderately tlnck epitlielial covering, in 

 which the nuclei ;ire indistinctly visible but the cell-outlines 

 scarcely visible at all, owing in a great measure to the diffuse 

 and strong staining of the cells as well as to the thickness of 

 the preparations. However, to judge from the arrangement of 

 the nuclei, we here evidently have to do with a single-layered 

 cylindrical epithelium. The epithelium appears on the whole 

 somewhat clearer than the internal cell-mass from which it seems 

 to be distinctly delimited. Whether it extends over all the 

 surface in equal thickness or distinctness could not be determined 

 with certainty. Often in one and the same larva it can not in 

 fact be perceived Avith jis much distinctness in one part as in 

 another ; this may be due as well as not to certain defects in 

 the manner of preparation. Frequently, but not ahvays, a clear, 

 irregularly granular layer is seen to cover the extei'ual surface. 

 I consider that layer to have been brought about by the deteriora- 

 tion of the flagella belonging to the epithelial cells, as the result 

 of the hardening process. — The internal mass is diffusely and 

 very strongly colored ; it shows closely crowded nuclei, around 

 which cell-outlines can not be defined with any degree of dis- 

 tinctness. A further insight into the histoloo'v could not be 

 obtained, all my sections being much too thick for that. Under 

 a moderately high power of magnification, the internal cell-mass 

 appears densely and uniformly granular, exactly agreeing in all 

 points with a larger archœocyte-congeries. From the latter, it 

 may be said, the larva in the early stage now being described 

 differs only in the presence of the peripheral epithelial layer. 

 And there exists nothing besides such archaeocyte-congeries to 

 which the origin of the developing larva can be traced back with 

 any degree of probaljility. For the enigma which follows this 



