ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
641 
was, in all specimens examined, found to be full of Bacteria. The young 
are fully formed before they leave the mother. The chief food of this 
new species appears to be Algae. When fully extended it measures 
1*4 mm. in length, the corona is 0*2 broad, and the body about 
0*18 mm. The species, which appears to be rare, was found near 
Cracow. 
Construction of Lorica of Brachionus.* — Mr. V. Gunson Thorpo 
concludes that the so-called dorsal surface of the lorica really consists 
of two plates — a “ dorsal ” and “ basal ” — and not of one antero-posteriorly 
curved plate, as is generally said. He directs attention to various cases, 
of which we may cite that of Brachionus from Colombo, in which the 
dorsal plate was distinctly prolonged, though to the very slightest extent, 
while the basal plate was well defined. The author thinks that the 
dorsal plate could not be so prolonged unless it and the basal were 
separately developed. 
Echinoderma. 
Excretory Organ of Sea-TJr chins. t — Herr F. Leipoldt describes 
the much- discussed “ dorsal organ,” which extends between the lantern 
and the madreporic plate of sea-urchins, and which many credit with an 
excretory function. The author’s researches refer to Sphserechinus granu- 
lans and Dorocidaris papillata , especially to the former. “ One thing 
may be stated with certainty, that the organ is no ‘ gland/ above all. no 
‘ kidney/ as P. and F. Sarasin maintain.” For there is no glandular 
epithelium, and no connection between the cavity of the organ and the 
body-cavity. Moreover, the author agrees with Leydig, that in stone- 
canal and madreporite the current is wholly inwards. The pigment 
masses, regarded by Hamann as evidences of an excretory function, 
seem to result from unusable or injurious substances which the wandering 
cells carry, and they occur in many other parts of the body. Nor are 
Kowalevsky’s experimental results accepted in proof of an excretory 
function. With Prouho, the author regards the dorsal organ as an area 
for the production of the amoeboid cells of the perivisceral fluid. 
Echinoderm Sperniatogenesis.f — Hr. G. W. Field gives a preliminary 
account of his comparative study of spermatogenesis in this group. He 
finds throughout a very general similarity, but considerable variation in 
minor details. The spermatogonia divide by mitosis to produce two 
spermatocytes, each of these again divides by mitosis to form two 
spermatids which, without further division, are directly changed into 
spermatozoa. In the nucleus alike of spermatogonium and spermatocyte, 
besides chromatin and karyoplasma, minute granules are found which 
seem to form the mitotic spindle. In the spermatid, on the other hand, 
similar granules are found not in the nucleus but in the cytoplasm. 
During the conversion of the spermatid into the spermatozoon the cell- 
membrane of the former becomes tightly drawn over the head of the 
spermatozoon, and as a mechanical consequence, according to the author, 
the granules fuse together to form a single large body, the Nebenkern. 
* Journ. Quek. Micr. Club, v. (1893) pp. 229-31 (6 figs.). 
f Zeitschr. f. wiss. Zool., lv. (1893) pp. 585-623 (2 pis.). 
X Anat. Anzeig., viii. (1893) pp. 487-93. 
