1921] NATURAL SCIENCES OF PHILADELPHIA. 127 



by the encystment of swimming naked specimens, which hardly 

 arriving into contact with the Zygnema, encysted directly, rather than 

 building their normal envelope. Plate VI, fig. 28, which also rep- 

 resents a cyst of Salpingoeca polygonatvm, such as I have seen several 

 times, formed during the night from specimens which had been seen 

 expanded the evening before, shows yet another kind of cyst. The 

 animalcules in these cases contract into a perfect spherule, yellowish 

 and shining, and besides a thin shell has been constructed also, but 

 balloon-like and without any opening at all. 



A few words might be added here, about the taxonomy. In 

 Salpingoeca, a very large genus and one which soon will become 

 much larger still, the form of the capsule is very constant, and fur- 

 nishes a very good — perhaps the only good — diagnostic character. 

 Now I could find nowhere such a description as might apply to the 

 species just described. It is very near to Salp. gracilis J. Clark, 

 but the capsule in that species is not cylindrical, being rather drawn 

 out into a long narrow point, which appearance I never could detect 

 in Salp. polygonatum. 



Salpingoeca lepidula sp. n. Plate VI, figs. 29-33; Plate VII, figs. 34-40. 



As stated in the preceding chapter, it is sometimes very difficult 

 to come to a precise determination of the species in the genus Sal- 

 pingoeca; and only after much hesitation have I come to the con- 

 clusion that the present form ought to be described as new. It is, 

 in fact, very nearly related to Salp. huetschlii Lemmermann, butin 

 this latter, the larger size as well as the more rounded and swollen 

 contour, and, more than all, the very considerable enlargement of 

 the cup -like opening, do not allow identification with the present 

 species. The affinity would be more evident with Salp. ampho- 

 ridiuni S. Clark, and also Salp. vaginicola Stein, at least as Burck (6) 

 figures them in his 1909 work,* but in these the form of the capsule 

 is not the same, being more like S. huetschlii in general appearance, 

 and having a narrow pedicle which is not present in Salp. lepidula; 

 this latter, also, always possesses two contractile vacuoles. 



However it may be, the species which we are now going to con- 

 sider was found covering in great quantities the threads of a Nos- 

 toccacean, itself abundant in one of the aquaria of the Zoological 

 Laboratory at Geneva. 



^ In Pascher's "Siisswasser-Flora" (27), these two species are figured on p. 82, 

 but with quite a different form from that given by Burck. It is quite possible, 

 indeed, that Burck had studied new forms, which it would have been advantge- 

 ous to give as such. 



