1889.] MICROSCOPICAL JOURNAL. 115 



Report upon the Postal Club Boxes — YT. 



By queen MAB. 



Box hd. One takes up the Cole Studies with a feeling of regret that 

 their publication should have been suspended. The text of this box, 

 " Lung of Duck " has no plate, and but a few words of written descrip- 

 tion. Speaking of tiie structure of birds it says that the bronchii do not 

 subdivide with the minuteness seen in the mammals: "The lungs of 

 birds are covered on their ventral surface only by the peritoneal mem- 

 brane, many of the principal branches run right through the lungs and 

 open into large delicate walled sacs in various positions among the 

 viscera, and send tubular prolongations into many of the bones ; thus 

 reducing the specific gravity of the bird and facilitating flight." 



No. 3 is the most interesting of the Cole Studies which have been 

 circulated for a long time, and is a transverse section, between the suckers 

 of the Liver Fluke, /^a^c/o/a hepaticjim. This object has been selected 

 because, for its size and low type of organization, it possesses a remarkably 

 well developed and complex reproductive S3'stem, and enormous repro- 

 ductive activity, and to practical agriculture especially as to its disper- 

 sion it has an important bearing. This fluke belongs to a class of tre- 

 matode worms which are parasitic, have flat unsegmented bodies, and 

 none of them exceed an inch or two in length. Its economic import- 

 ance is derived from its casual relation to the liver rot in sheep, which 

 has to so great an extent proved fatal. This same species has been 

 found in man. Other species infest various animals, as oxen, horses, 

 dogs, deer, etc. Apart from its reproductive system, which occupies 

 nearly the whole of the body, the organization of this Fasciola is very 

 simple. The lateral margins of the body and whole posterior portion 

 are occupied by a pair of very ramifled vitellaria or yelk glands. A 

 smaller organ, the shell gland, secretes the yellow horny material with 

 which the eggs are invested. The developmental cycle through which 

 the embryo passes before it attains maturity is strange. The fluke 

 presents the phenomena of alternate generation and heterajcism in a 

 very complete form. Between the free Qg<g and the vertebrate inhabit- 

 ing adult fluke, a number of intermediate and dissimilar forms occur, 

 and for the support of some of these an invertebrate host is essential. 

 At least three generations are necessary to produce the original 

 form. vSomething of this life history is as follows : 



Generation A. i. The egg is laid in an oval yelldw horny case, 

 by the e.^^ gland. At one end a sinuous line marks out a portion which 

 serves as an operculum, and is later cut ofl' for the liberation of the 

 embryo. A hundred or two flukes inhabit the bile ducts, distending 

 them enormously, hundreds of thousands of eggs are laid by a single 

 fluke, and as they are discharged they pass out of the bile duct into the 

 intestine and thence with the faeces out of the body. The development 

 of the eml)ryo with the proper temperature requires two or three months. 

 When ready to emerge, the embryo among other investments is provided 

 with cilia, which however do not move until the shell is burst. 



2. Free embryo. By a vigorous extension of its body the embryo 

 throws off' the operculum, and on contact with water on the damp grass 

 the cilia begin to move and the embryo swims about actively. An in- 

 termediate host now becomes necessary, else the embryo soon dies. 

 A small semi-aquatic snail, Lymmius truncatulus. has been found to be 



