IN THE LARV^ OF ANISOPTERID DEAGONFLIES. 173 



forms a highly specialized portion of it. Its protoplasm is only very slightly 

 chromatophil, clear, very slightly granular, and having embedded in it a 

 series of comparatively enormous nuclei (nui), besides a smaller number of 

 much smaller nuclei (nu^)- There is absolutely no indication of separate 

 cell-territories in this mass. On its external side it is covered by a con- 

 tinuation of the fine cuticle which everywhere overlies the rectal epithelium. 

 On its inner side, it is contained by a very delicate basement-membrane 

 separating it from the adjacent mass of hypobranchial tissue. 



The most noticeable feature in the structure of this pad is the abundant 

 fibrils which cross it transversely from side to side. Many of these fibrils 

 are seen to be fittached to the nuclei, and therefore clearly do not represent 

 cell-limits. Wherever the pad is bent or creased, there may be seen 

 particularly strong fibrils arising, sometimes in groups, to pass out diverg- 

 ingly across the pad. Generally, a number of fibrils pass out from each 

 nucleus and tend to diverge as they approach the border of the pad. The 

 spaces between the fibrils are clear for the most part, appearing slightly more 

 granular towards the edges of the pad. The whole appearance of these 

 spaces suggests a state of turgidity, and they are very probably filled with a 

 liquid of some sort, the actual protoplasm of the pad being confined to the 

 nuclei, the fibrils, and the granular substance which lies close to the borders 

 of the pad. 



The large nuclei, which I propose to term the meganuelei of the basal pad 

 (nui), are rather unevenly scattered through the pad. In AustrogompKus, 

 one finds the greater number of them lying rather closer to the external 

 than to the internal border of the pad. In that part of the pad which lies 

 on the rectal circumference, they tend perhaps to lie even more unevenly, 

 for one not infrequently sees one, or two close together, lying fairly close to 

 the basement-membrane. Throughout the pad, there seems to be a tendency 

 for two or three meganuelei to approximate together ; so that, in any given 

 section, one meets with several cut through very close together, forming as 

 it were a centre of radiation for numerous fibrils, and followed by a space in 

 which no nuclei are visible. 



These meganuelei are all of a somewhat elongate-ovoid shape, showing in 

 a cross-section of the pad an elliptical section with its major axis transverse 

 to the pad, and in longitudinal section of the pad a circular or nearly circular 

 section. Hence they are, in actual shape, elongate prolate sjjiieroids, with 

 their axes directed transversely across the pad at right angles to its internal 

 and external borders. If we suppose the basal pads to have been formed by 

 the absorption of some liquid into the protoplasm of a portion of original 

 typically flat epithelial syncytium, in such a way that the swelling took 

 place everywhere generally at right angles to the plane of the epithelium, 

 both the fibrils and the nuclei would become extended in the direction in 

 which we here find them. It seems then probable that the meganuelei were 



