'306 H - JAMES-CLARK ON THE AFFINITIES OF SPONGES. 



rality " of the contracting vesicles does not alone belong to the PMzopoda, but, as I shall 

 show hereafter, 1 that it is also to be observed among the true Flagettata; and I would 

 remark, moreover, that when we consider the close relationship — which I hope to prove 

 in this paper — of the Sponge to the other flagellate, monad-like infusoria, which undoubt- 

 edly have a definite oral aperture, we must, if on no other grounds, conclude that it also 

 possesses a true mouth. 



Still there would appear to be some who doubt whether, after all, the Sponges are really 

 animals instead of plants, and, moreover, seem to insist that they are neither the one nor 

 the other, but form, with other infusorians — such as Volvox, Gonium, Pandorina, Euglena, and 

 other conferva-like bodies — a group by themselves, standing intermediate to, and partak- 

 ing of the nature of, both animals and plants. This is the group which has been called 

 Phgtozoa, i. e. plant-animals. 



In the midst of this halting decision, I have been, for some years past, working upon a 

 class of infusoria, the knowledge of whose structure fully prepared me not only to recognize 

 the animal nature of the Sponge, but also enabled me to determine to what group of Infu- 

 soria it belongs. Such a decision, therefore, does not leave any trace of doubt in my mind 

 as to the strictly animal nature of the Sponges. The whole question in dispute hinges upon 

 the determination as to the animal or vegetable nature of the Monad-like, or "so-called 

 flagellate infusoria. And here again I would say that it has fallen to my lot to decide, for 

 the first time,^ that one of the smallest known of the infusoria, the Monad, (Moms termo, 

 Ehr ?) is an animal. If, now, we can prove this point, the way is perfectly clear through the 

 intermediate forms which lie between the Monad and the Sponge. 



Commencing, then, with what I believe to be the Monas termo of Ehrenberg. I shall pro- 

 ceed to describe in detail a series of forms — several of which are new, both generically 

 and specifically — which stand in the closest relationship among the lowest embodiments 

 of infusorial life, embracing among them, as I hope to show, the true ciliated sponges, and 

 which, notwithstanding, lead in unobstructed, although varied courses, 8 to the more elevated 

 kinds of Protozoa, the true Infusoria Oiliata. 



§ 1. Monas termo, Ehr ? 

 (Plate IX., figs. 1, 2, 3, 4.) 



Upon a slight acquaintance with this infusorian, one would be strongly inclined to iden- 

 tify it with the younger stages of Arihophysa Mullen. Bory. (fig. 49) ; but a more searching 

 investigation reveals such a number of characters in each which are not to be found in the 

 other that one need not have any hesitation whatever in setting them down as totally di- 

 verse organisms. In fact, Monas belongs to the uniciliate Flagettata, whilst the other genus 

 just mentioned is a biciliate, heteronematous form. 



Monas lives in two diverse conditions, of which one is a fixed state (fig. 3), and the other 

 a free and motile stage (figs. 1, 2, 4). During its sedentary life it may be found in great 

 abundance on the old stems of Myrwphyllum, Potamogeton, Ceratophjllum, and other aquatic, 

 phenogamous plants which inhabit quiet waters, and are more or less thickly covered by a' 

 floccose overgrowth of various minute Conferva'., Diatomacece, etc. In its free state it swims 

 with either a sort of hitching, wriggling motion, or, gliding along smoothly, revolves at an 



1 Salpingmca marinus, nov. sp. § 8, and S. amphoridium, nor. sp. § 9. 



2 See the preliminary remarks upon Anthophysa, §11. 



