100 Dr Gairdner's Analysis of 



contractions and contortions of the animal ; when the connexion of the 

 different sacs with the intestinal canal becomes very apparent. 

 Fig. 5. Represents the structure and development of the Vorticella Convallarioy 

 MUller. In consequence of ignorance of this, no less than six differ- 

 ent species have been formed of this animal, according to its appear- 

 ance at different stages of its development. 



At a appears a network of innumerable minute points attached to the 

 roots of the adult animal. Their size is about To5?r"'* They expe- 

 rience a vibratory motion, but are never detached from their original 

 seat, so that they are probably connected with the roots by fine pe- 

 duncles, too minute to be visible. They closely resemble the net- 

 work of ova, whose actual exclusion from the parent animal, Dr 

 Ehrenberg has frequently seen in the Kolpoda cucullus. Their actual 

 production from the adult V. convallaria has never yet been seen, but 

 this analogy makes it more than probable they are of the same nature, 

 or, at most, the very next grade in the progressive development of the 

 animal. 



At b the same animal is seen further advanced, and already furnished with 

 a distinct peduncle and head, the latter of which is even now capable 

 of causing currents of coloured particles in the water. Schrank gave 

 to the animal under this form the name of V. monadica.f Still later 

 they appear as at c, where the spiral shortening of the peduncle is most 

 apparent. 



At d the animal is in its perfect state. We need not repeat here what we 

 have already noticed, of this animal propagating itselt also by a longi- 

 tudinal and transverse division, and also by gemmules. 

 Fig. 6. Lateral view of the Hydatina senta, Ehrenberg, Vorticella senta, Mml- 

 ler, magnified 380 diameters, the true length of the animal being 

 about i"'. 



a External tunic of the integuments. 



b Internal ditto.' 



e Bifid tail. 



d Intestinal canal. 



* (Esophagus. 



/ Bulb of the oesophagus. 



g One of the glandular bodies which embrace the oesophagus. 



h Rotatory organs. When seen vertically, whilst in full activity, they are 

 seventeen in number, and each is provided with six ciliae. 



i Ligamentous bands, to which the rotatory organs are attached, and by 

 which their motions are regulated. 



k Mouth, with its mandibules or teeth. 



I Cloaca communis for the intestine and oviduct, 



m Orifice of the anus. 



n Caudal muscles. 



o Musculus dorsalis anterior. 



p Musculus dorsalis posterior. 



q Musculus lateralis dexter anterior. 



