894 SUMMARY OF CURRENT RESEARCHES RELATING TO 



teristic as to serve all purposes of identification until the internal 

 structure can be fully described. 



Mr. F. W. Phillips also records* and figures a species of 

 BracMonus which he believes to be either a variety or an undescribed 

 species. It most resembles B. Baker i, but differs in the arrangement 

 of the granules and the position and shape of the spines. It was 

 found at Hertford Heath, and in such vast numbers as to render the 

 water turbid. 



Observations on Rotifera (Melicerta).t — The following observa- 

 tions were made by M. L. Joliet on Melicerta ringens and an allied 

 species which is distinguished by the presence of a long thread that 

 fixes it in its case. Save in some details, the remarks concerning one 

 are applicable to the other. 



Nervous System. — Several authors have followed Huxley in the 

 statement that the ganglion of Melicerta is situated near the mouth, 

 and consequently on the opposite side of the body to the anus. This 

 would be the converse of what exists in all rotifers. In reality what 

 these observers have taken for a ganglion is a gland, both in its 

 structure, situation, and functions. The true nervous centre is on 

 the opposite side, on the dorsal face of the pharynx. It is composed 

 of a group of large, characteristically formed ceils, with a large 

 nucleus. Several similar cells are disposed on the sides of the 

 former and spread in different directions. This centre somewhat 

 resembles that described by Leydig in Lacinularia. It is not large, 

 and M. Joliet thinks that in many rotifers the relatively enormous 

 ganglia that have been described are glands, and that the true nervous 

 centre has yet to be found. In any case the anomaly thus created for 

 Melicerta does not in fact exist. 



Beproduction. — During the whole of the summer three kinds of 

 eggs are found in the tubes which the animals inhabit : the male 

 summer-eggs, which are the smallest and which have not been noticed ; 

 the female summer-eggs, which arc larger ; and the yet larger winter- 

 eggs, extremely opaqiie when laid, and later on becoming encysted in 

 an ornamented chitinous membrane within the first chorion. These 

 different eggs are not laid by all the females indiscriminately, but 

 each one has, so to say, its speciality. 



Formation of the Egg. — All the eggs in the ovary have a uniform 

 aspect and appear equally developed, with the exception of a single 

 one which, detached from the ovary and placed in that portion of the 

 enveloping membrane that may be termed the maturation pouch, is 

 always extremely granular and enlarges with such rapidity that in 

 less than twenty-four hours it attains a volume more than fifty times 

 greater than that which it had preserved for several weeks in the 

 ovary. This is explained by the fact that the stroma of the genital 

 gland perpetually secretes a large quantity of granules of deuto- 

 plasm. These granules the free egg agglutinates with rapidity and 

 mixes with its own vitelline substance. In certain Floscularice, in 



* Trans. Hertfordshire Nat. Hist. Soc, i. (1881) p. 118 (1 fig. of a pi.), 

 t Cnmptes Rcndus, xciii. (1881) pp. 748-50. 



