NOTES AND MEMORANDA. 393 



tlie walls of tlie dome, while each sends off a long filament 

 to the region where the alimentary canal begins to bend 

 downwards towards its ab-oral termination. The great apical 

 ganglion supports two sessile ocelli, with pigment and lens, and 

 two small spherical vesicles, each containing a clear spherical 

 corpuscle. These last the author regards as auditory capsules. 



A system of vessels was also described. This consists 

 mainly of a sinus which surrounds the great apical ganglion, 

 and sends off three branches, which run in a radial direction 

 in the walls of the dome, two lateral and one ab-oral, and 

 appear to open into a sinus which surrounds its base. 



In the progress of development the ab-oral end of the 

 alimentary canal becomes elongated in the direction of the 

 axis of the dome, carrying with it the walls of the base of 

 the dome, which are to form the proper body walls of the 

 future worm, and in this way a long cylindrical appendage 

 becomes developed, and hangs from the central point of the 

 base. At first there is no trace of segmentation, and this is 

 subsequently induced on the cylindrical body of the worm 

 by the formation of consecutive annular constrictions. 



The process of development, as observed by the author in 

 the species of Mitraria examined by him, thus differs in 

 several points from that observed by Mecznikoff. Among 

 these the most important is that the ventral side of the worm 

 is formed simultaneously with the dorsal instead of sub- 

 sequently to it and independently of it, as in the case 

 described by Mecznikoff. The development of the worm 

 was not traced to the ultimate disappearance of the dome- 

 like body of the larva. 



2. On some Points in the Development of Vorticellidae. By 

 Prof. AUman. — The author described, in a beautiful branched 

 and clustered vorticellidan, a process different from any 

 which had been recorded by those observers who had 

 described the so-called every day process, and the behaviour 

 of the " nucleus" in the Vorticellidse. 



In almost every cluster some of the zooids composing it 

 had become greatly altered in form. They had increased in 

 size, and instead of the bell-shaped form of the others had 

 assumed a globular shape, and had lost both oral orifice and 

 ciliary apparatus, while their supporting peduncle had 

 ceased to be contractile. In the younger ones the contractile 

 space of the unchanged zooid was still very evident, but 

 was fixed, showing no tendency to alteration of size, and the 

 so-called nucleus was very distinct and larger than in the 

 ordinary zooids. The whole was enveloped in a transparent 

 gelatinous-looking investment. 



