1891.] MICHOSCOPICAL JOURNAL. 243 



which process some young ones ready to mature are always on hand 

 to replace older ones, products of previous divisions, which fall out of 

 their places and give room to the younger ones. In this way of look- 

 ing at a tissue we see it is like a haliitat tenanted with Amcsbae. Though 

 fatal circumstances may at any time remove large numbers of AmoDbJE 

 those that are left by division soon fill their places, and so it happens in a 

 tissue that though the cells are constantly being lost new ones are as 

 constantly coming up to replace. It is in this way that the tissues are 

 constantly changing and the body is truly, as often said, a wholly new 

 body after a certain time, which, however, must vary very much for 

 di fit" rent organs. 



It is thus perfectly rational to look upon the ciliated epithelium as a 

 tissue that is an aggregate of cells all alike in form and function, and 

 its work as the resultant of the individual works of the component 

 cells, and it is further perfectly reasonable to compare the ciliated cell 

 with a unicellular animal like Vorticella, a near ally of Amoeba, and to 

 notice that its work is not at all absolutely unlike that of either of these, 

 but in reality a special exercise of one of the powers among the sev- 

 eral unspecialized powers of Amoeba. In other words, we do not find 

 in our study of ciliated tissue any positively unique and new phenomena 

 of cell life, but only special applications to particular conditions. 



(To be continued.) 



The First Diatoms Published. 



By ARTHUR M. EDWARDS, M. D.. 



NEWARK, N. J. 



As it may interest your readers to know, I find in Vol. 23 of the Phil- 

 osophical Transactions of the Royal vSocietv of London for 1704 '' two 

 letters from a gentleman in the country relating to Mr, Leewenhoeck's 

 letter in Transactions, No. 2S3, communicated by Mr. C." In the let- 

 ter of June 21, 1703, is a description and four figures of " a creature " 

 which is evidently Hydra fusca. VVe found it in clear water, "which I 

 took from the ditch at W., in. which, with my utmost attention, I could 

 discover no more than this one of the same kind. Fig. i represents it 

 in one of the postures it appeared the first day (for it varies every mo- 

 ment), and the knob at a, which looks like the gut coeciivi was some- 

 times a little more lengthened ; two or three days after I could per- 

 ceive two or three white fibres at the end of it, and on the fourth day 

 the animal, lying stretched at its full length, appeared as in Fig. II, and 

 I plainly saw that what I thought an excrescence was a young one, with 

 six horns coming out of the side of the old one, and next day I found it 

 in water entirely separated from the body, and was about one-third the 

 length of the parent." " The horns are perfectly white, and the body 

 yellowish." Although neither the " gentleman from the country " 

 nor " Mr. C." are named, we have here a first with Leewenhoeck's, 

 the first communication of the discovcfiy of Hydra fusca. Leewen- 

 hoeck's discovery of /^yrt^ro! fusca is in the Philosophical Transactions 

 for January and February, 1703, is dated at " Delft, in Holland, 25 Oc- 

 tober, 1702." He describes and figures Lemna polyrr/iiza, as seen by 

 him. On the roots of levina are figured Vorticella., Limnias.i and a 

 Diatom, Synedra., as the roots " were also overgrown with a great 



