50 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the central cells first ; then the sucker begins to appear, and is followed 

 by tbe pharynx and enteron, excretory organ, and nervous system. The 

 larva now undergoes a double ecdysis, but the cuticle is not lost but 

 forms a protective covering uutil the Distomum lias passed into the 

 intcstino of the bird. Between it and the cuticle a serous fluid collects, 

 and it is to this that the animal owes its elasticity and its freedom from 

 injury in its host's gizzard. 



By feeding experiments, the author found that the Sylviidte are the 

 true hosts of Distomum macrostomum. One or two days after feeding the 

 parasites were found in the cloaca, which is their permanent seat. About 

 the eighth day egg-production began, and after fourteen days the 

 Distomum was full of eggs. 



With regard to the early stages of egg-development, Herr Heckert 

 confirms the results of Schauinsland ; the final result of segmentation is 

 the formation of an embryo with a very thick shell ; it is about 1/30 mm. 

 long, and consists of only a few cells ; at the hinder end of a ciliated 

 comb there is a powerful cone which acts as a steering organ. 



Owing to failures in further breeding, the author came to the conclu- 

 sion that the eggs must be eaten by the snail, and the embryos set 

 free in their stomach by mechanical or chemical influences. After 

 feeding Succinese with the eggs, he found that the embryos became free 

 in about a quarter of an hour after eating ; they swim about in the 

 stomach and attempt to bore with their head-cone. After eight days, 

 the first stages of the sporocysts were found in the liver, where they 

 were in the form of small rounded spheres with more or less well- 

 marked elevations, which are the first signs of the commencing 

 branches. 



Temnocephala.* — Mr. W. A. Haswell gives an account of an aberrant 

 monogenetic Trematode found on the large fresh-water crayfish of the 

 northern waters of Tasmania. It is a leech-like animal about half- 

 an-inch long ; at the narrower anterior end there are on either side two 

 very long and slender tentacles, which, when fully extended, are one-half 

 or two-thirds the length of the body. In the species from New South 

 Wales or New Zealand there are five equal slender tentacles. The 

 rapidity of the movements, and the extreme sensitiveness of the animals 

 are surprising ; in turning aside from a touch they show a very definite 

 sense of direction. The author distinguishes four species which he calls 

 Temnocephala fasciata (on Astacopsis serrata, streams of New South 

 Wales) ; T. quadricomis (on A. Franklinii, northern rivers of Tasmania) ; 

 T. minor (on A. bicarinatus, streams of New South Wales) ; and T. novse- 

 zealandise (on Paranephrops setosus, rivers of New Zealand). 



Temnocephala is regarded by Mr. Haswell as most nearly related to 

 the Tristomidse, but the numerous peculiarities which it presents require 

 the formation of a new family for its reception. These characters are the 

 possession by the cephalic end of the body of slender filiform tentacles 

 with prehensile and tactile functions ; as the tentacles are adhesive they 

 take the place of the anterior suckers ; their adhesive powers are 

 increased by the secretion of certain special unicellular glands. There is 

 a single large radiated posterior sucker without hooks. A rudimentary 

 segmentation is indicated by the incomplete transverse dissepiments 

 which are formed by specialized portions of the parenchyma muscle, 



* Quart. Journ. Micr. Sci., xxviii. (1887) pp. 279-302 (3 pis.). 



