ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 619 



Protozoa which the writer institutes is the important conclusion 

 that in the nucleus of the Rhizopoda, just as in that of other Protozoa, 

 we have to do with a typical cell-nucleus. 



Observations on the Gregarinidse.* — Dr. 0. Biitschli jBnds that 

 Schneider is not correct in denying that there is true encystation and 

 copulation in those Gregarines that unite by pairing ; in the larva of 

 the cockroach he found a large number of cysts, and all stages 

 between them and the elongated pair of Gregarines ; when encysta- 

 tion is about to take place the individuals of a pair shorten and grow 

 wider, so that the oval gradually passes into the spherical form ; an 

 investment is formed for the pair before their individuality disappears, 

 proving distinctly that the cysts are formed of two individuals. 

 The transparent investing layer becomes more apparent by the attach- 

 ment of foreign particles to its surface ; the conjugating animals 

 rotate continually, and form more and more a single sphere ; the 

 anterior ends (protomeres) of each individual are still distinct. As 

 the gelatinous investment increases the true envelope of the cyst 

 becomes developed below it ; the rotation of the cyst's contents 

 begins to slacken, and there is a change apparent in the boundary 

 line between the two individuals : the true envelope becomes much 

 thicker ; and the whole cyst takes on the characteristic ovoid form. 

 These changes occur within the space of an hour and a quarter. 



Further observations are more difficult on account of the loss of 

 transparency, but the author has been able to observe the somewhat 

 sudden disappearance of the protomerite in the deutomerite, and the 

 fact that complete fusion of the two individuals does not take place 

 until forty-eight hours after the commencement of encystation and 

 after the cyst has with the faeces left the digestive canal of the host ; 

 pseudonavicellse begin to be formed long before the fusion is complete. 

 Partial fusion may, however, have gone very far ; we can only judge 

 that it is complete when the line of separation disappears from the 

 surface. The author states that in a very young pseudonavicella he 

 has distinctly seen a nucleus, excentric in position, and with pale, not 

 granular contents ; these nuclei appear to arise from the peripheral 

 nuclei which are formed during that process of gemmation which 

 leads to the development of pseudonavicellse. From his observations 

 on the " sporoduct," the author concludes that the clear non-granulated 

 cords are formed by the separation from one another of granules in the 

 peripheral portion of the contents of the cyst ; in this axis of the 

 cord the finely granular plasmatic plexus becomes arranged in tubular 

 fashion, and within this tube the true sporoduct is formed ; the number 

 of these varies with various cysts, and appears to be closely connected 

 with the size of the cyst itself. 



After a further discussion of this subject and a reference to the 

 development of the young Gregarines, the author passes to the Mono- 

 cystis which is found in the earthworm ; and dealing with the question 

 of the mode of attachment of M. magna, he states that he found each 

 imbedded by its somewhat narrow end in a very large ciliated cell 



* Zeitschr. f. wiss. Zool., xxxv. (1881) pp. 384-410 (2 pis.). 



