ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 971 



the cilia of the sporocyst alone remain. The number of beats of the 

 vacuole of the dividing cyst remain normal, since fresh water can be 

 constantly forced into the body by the orifice ; in the lasting-cyst the 

 number rapidly decreases and becomes zero, as the cyst-wall hardens and 

 no more can enter. In the sporocyst the number of beats remains un- 

 altered, but as there is no orifice in the cyst-wall by which fresh water 

 can enter, the volume of the body of the animal diminishes, and an inter- 

 mediate space appears between the cyst (velum) and the animal, and into 

 this the vacuole-water is driven. The further changes which appear in 

 the dividing cyst are the formation of walls and nuclei for the divided 

 parts, and new formation of vacuoles in the parts of the dividing- cysts. 

 In the sporocyst the volume of the body diminishes to one-eighth of its 

 original extent, while the nucleus and the pellicula disappear. New cilia 

 next become formed in the dividing cyst, and two or four parts swarm 

 out by the orifice ; the thickened protoplasm of the sporocyst becomes 

 completely homogeneous, and a second cyst-wall (the true sporocyst- 

 wall) becomes excreted. The characters of a complete dividing cyst are 

 a simple wall with an orifice at one pole, several parts (two to four) 

 in the cyst, nutrient spheres, assimilation-corpuscles, and a normally 

 pulsating vacuole ; those of the lasting-cyst are a simple (generally thick) 

 wall without any orifice, one animal in the cyst, assimilation-corpuscles, 

 but no nutrient spheres, the vacuole does not pulsate, and is either dilated 

 or compressed and invisible. The sporocyst has double walls and no 

 orifice ; its contents are completely homogeneous and opalescent ; there 

 are no nutrient spheres, assimilation-corpuscles, or pulsating vacuole. 



The object of the dividing cyst is protection during the formation of 

 two or four parts, and its duration is from two to twelve hours ; that of 

 the lasting-sphere is protection from drying, and its duration one to four 

 hours. The sporocyst is for the formation of spores, and lasts from 

 a half to one hour. 



The development of Golpoda shows that the " biogenetic fundamental 

 law " applies to the Monoplastida, for we have (1) a non-nucleated 

 spore-stage, (2) a multinuclear, and then (3) a uninuclear amoeba- 

 flagellate stage, and (4), finally, the young Golpoda. This form is a 

 very primitive Ciliate ; the structure of the nucleus of Golpoda steinii is 

 throughout life vesicular, and has just the appearance of the nucleus of 

 a Flagellate, while the division in cysts is perhaps also a sign of affinity 

 with the Flagellata. In the mode of formation of its spores Golpoda 

 exhibits many signs of relation to the Gregarinida and Coccidia, as in 

 the disappearance of the nucleus and the formation of a double wall of 

 ency station. 



Ciliary Movement.* — Dr. J, Clark in investigating the effect of 

 reduced oxygen pressures on the streaming movements of protoplasm, 

 has also made some interesting experiments in regard to the influence of. 

 the same condition upon cilia. Removal or reduction of the oxygen 

 caused Ghlamydomonas, Eiiglena, &c., to pass into the resting stacre. 

 Eeturn of oxygen recalled them to activity. Pleurotricha, Stylonychia, 

 Paramsecium required less than 1 mm. oxygen pressure to revive them ; 

 others even less. He describes an interesting experiment with a Stt/lo- 

 nycMa, which, at a temperature of 17*2^ C, was brought under a 

 pressure of 2 • 5 mm. In four minutes it became quiescent, and rapidly 



* Ber. Deiitsch, Bot. Gesell, vi. (1S88) pp. 273-80. 



