ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
349 
cause of the association of specimens of Phymosoma with coral islands, 
but it is to be observed that several species make their homes in tubular 
holes burrowed in the soft coral rock. 
0. Nemathelminth.es. 
Gordius tolosanus and Mermis.* — Dr. v. Linstow corroborates his 
discovery that the beetle Pterostichus niger is the host of the larval 
Gordius tolosanus Duj. As the pools in which the Nematodes are found 
dry up in summer, it seems that the beetles must repopulate them each 
spring. In the spring months the beetles fall into the pools and are 
drowned ; from their bodies the nematodes pass into the water. Trout 
and some other fishes occasionally contain these parasites, which is 
readily explicable on the supposition . that the fishes have devoured 
infected beetles. Meissner observed the larvae of Gordius tolosanus 
boring into Ephemerid larvae ; it is perhaps in the Ephemerids that the 
parasites leave the pools and are eaten by beetles. The life of this 
nematode is annual. The sexual union, which Meissner observed, may 
take place in April ; the females deposit the eggs in snow-white strings 
on the stems of water-plants ; the development is completed in about 
four weeks. The structure of the larva is described, and von Linstow 
adds some details to his previous account of the adults. He also reports 
his discovery of the larvae of Mermis crassa in the aquatic larvae of 
Ghironomus plumosus. In Hyalina cellar ia, the larva of Mermis Hyalinse 
was found, a fact of interest since only two other instances of Molluscs 
as hosts of Mermis are on record. 
Arabian Nematodes.! — Mr. N. A. Cobb has collected more than two 
hundred marine Nematodes from the coast of Arabia, among which seven 
distinct species have been recognized; all may be referred to genera 
known to inhabit Atlantic waters. The author proposes a system of 
formulae which reads thus for a species of Oncholaimus : — 
1 - 8 - 2 - 17 - 2 - 52 - 93-3 *8 8 - 16-6 M 94*1 i or 
•9 1*5 1 - 6 - 1*7 • 8 1 ' 7 *8 1 - 31-414 -8 1>85 
These numbers refer respectively to the pharynx, nerve-ring, base of 
neck, vulva, and anus ; M stands for male ; the numbers above the 
horizontal line relate to longitudinal and those below it to diametral 
measurements. Beading the formula from left to right reads off 
the dimensions of the animal from head to tail. The peculiarity of the 
formula is that the unit of measurement is not absolute but relative, 
being nothing else than the hundredth part of the length of the worm 
itself. The absolute length of the animal expressed in millimetres is 
put to the right. Mr. Cobb urges various recommendations for this 
formula, and expresses a belief that by averaging the specific we may 
get a generic formula. The seven new species found are fully described. 
Echinorhynchus polymorphus and filicollis.f— Prof. M. Braun gives 
reasons for thinking that E.jilicollis Bud. is not, as is now generally 
* Arch. f. Mikr. Acat., xxxvii. (1891) pp. 239-49 (1 pi.). 
t Proc. Linn. Soc. N.S.W., v. (1890) pp. 449-68. 
X Centralbl. f. Bakteriol. u. Parasitenk., ix. (1891) pp. 375-80. 
1891 . 2 b 
