INVERTEBEATA, CRYPTOGAMIA, MICROSCOPY, ETC. 587 



ovum. The first cleavage furrow is vertical, tlio second equatorial, 

 the egg becoming divided into two micromeres and two macromeres. 

 Both of these undergo further multijjlication, and the micromeres 

 gradually grow round the macromeres (epiboly), forming the epiblast 

 or primitive ectoderm, while the included macromeral cells constitute 

 the hypoblast or primitive entoderm. 



The solid oval embryo thus formed elongates until it acquires a 

 fusiform shape ; the two ends of the spindle being the rudiments of 

 the first two tentacles. The gastro-vascular cavity is formed as an 

 excavation in the solid mass of endoderm. 



The author furtlier traced the changes by which the newly freed 

 larva (Actinula) is converted into the attached Tuhdarin polyp ; he 

 describes the gradual differentiation of the larval body into hydrocaules 

 and hydrorhiza, the formation of the perisarc, &c. 



Protozoa. 



Tintinnus semiciliatus, a new Infusor.* — Dr. V. Sterki de- 

 scribes a new species of the genus Tintinnus, found by him at 

 Schleitheim, in Switzerland. 



The body is of a wine-glass shape, truncated anteriorly, and behind 

 passing gradually into a long stalk by which it is attached to the 

 bottom of its tube. The animal was sometimes found witliout its 

 tube ; whether this was an accidental or a normal state of things is 

 uncertain ; when free the stalk was always wanting, the posterior end 

 of the body being rounded off, or, at most, was represented only by a 

 small stump. In some cases a constriction was observed near the 

 posterior end of the body ; probably this was due to pressure, not to 

 commencing division. The length of the body without the cilia is 

 0-04 to 0-06 mm., with the stalk 0-1 to 0-12 mm., the diameter 

 • 03 mm. 



The anterior end of the body is surrounded by a raised circular 

 rim of firm consistency, from which spring the fifteen to twenty large 

 adoral cilia or membranelles, each of which is flat and band-like, 

 inserted obliquely on the rim, and split up distally into about six 

 filaments. Eound the inside of the rim, near its base, is a row of 

 shorter, fine cilia of the ordinary character, and perhaps homologous 

 with the paroral cilia of Oxijtrichina. | Also the anterior or free half 

 is sparsely covered with short, fine cilia. 



Within the ciliated rim, the anterior end of the animal is slightly 

 convex, quite soft, and presents an irregular depression or peristomial 

 space, without, however, any distinct mouth or gullet. Neither cilia 

 nor undulating membrane occur in the peristome, but its inner wall 

 undergoes continual movement, acting like a sort of lip or tongue. 

 This fact is interesting as showing the possibility of independent 

 movement on the part of the soft endosarc or internal parenchyma. 



The body-substance is clear and slightly yellowish. There are no 

 muscle-strife, and no discoverable structure in the stalk. In the 

 posterior end of the oval nucleus is a strongly repeating globular 



* ' Zeitschr. wiss. Zool.,' xxxii. (1879) p. 4G0. 

 t See this Journal, ii. (1879) p. 91. 



