772 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The next form examined is Spirochona gemmipara, wlrich lias been 

 carefully studied by Hertwig. Some additions to our knowledge are 

 made, especial attention being given to tbe conjugation of tins species. 



Lagenophrys ampulla is a Vorticelline which does not appear to 

 bave been studied since it was described by Stein. There is no 

 specially differentiated cortical layer, but tbe protoplasm of fresh 

 specimens exhibits very lively streaming movements, which cease if 

 the animal is kept under unfavourable conditions. Two parts are to bo 

 distinguished in the oesophagus, which are separated from one another 

 by a constriction which varies in width at various times. Just in 

 front of the left wall of the anterior portion there is a long seta which 

 appears to serve as a tactile organ. The sausage-shaped nucleus is, 

 as a nilc, finely granulated, but contains sometimes a number of 

 nucleoli. A spindle-shaped or rounded nucleolus is always attached 

 to it, but is not constant in position. The species is only produced 

 by a process of fission, which has been accurately described by Stein. 



In his fourth chapter the author discusses the essential nature of 

 conjugation, and the significance of the nucleoli in the ciliated Infu- 

 sorians. There are a great number of variations in the phenomena of 

 conjugation, and it is as yet impossible to say why, in one Infusorian 

 the nucleus breaks up, and in another is wholly or partially retained. 

 The object of conjugation appears to be the restoration of the balance 

 between the cyto- and nucleo-idioplasm. This is effected by the 

 respective changes which take place between two individual infuso- 

 rians. In many cases only those ciliates conjugate which have not 

 attained the normal size. It is conceivable that while, during re- 

 peated divisions, the cytoplasm may be sufficiently well nourished, 

 nucleo-idioplasm may be insufficiently so. There are observations 

 which support the supposition that the idioplasm of the cell may pass 

 over into that of the nucleus. The hypothesis suggested explains why 

 it is that conjugation periodically alternates with division, and why the 

 nucleus undergoes such deep-seated changes. Conjugation appears, 

 in a very striking way, to be epidemic, or, in other words, to affect a 

 large number of individuals at the same time. This is possibly duo 

 to a sudden alteration in their external relations. 



In the fifth chapter the author gives an account of Calidina 

 parasitica, with remarks on the Philodinaidpe. The members of this 

 group differ from all other fresh-water Rotifers in a number of 

 characters, and if the group be called the Aductifera, and the rest the 

 Ductifera, we may say that in the Aductifera the gonads are double 

 and consist of two completely closed sacs without efferent ducts. In 

 their continuous yolk-mass there are a number of ovarian nuclei. In 

 the Ductifera the generative apparatus is single ; there is a special 

 efferent duct opening into the cloaca, and the germinal is distinct 

 from the vitelline portion of the ovary. In the Aductifera the wheel- 

 organ has still the primitive form, and consists of two ciliated circlets 

 placed one behind the other. Dorsally the body is prolonged into a 

 long retractile proboscis which is provided with a second ciliary 

 apparatus at its auterior end. In the Ductifera the primitive form of 

 the wheel-organ is greatly and variously modified in various species ; 



