ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 581 



of the daughter-chromosomes from the maturation division becomes 

 extruded from the cell, so that the polar body contains no cytoplasm, 

 but consists of a portion of the nucleus surrounded by a double mem- 

 brane. The mitosis in this form resembles closely that occurring in the 

 Protozoa. The two micromercs which represent the ectoderm, are given 

 off from the single macromere (mesoderm) in the first two divisions. 

 The gastrulation is epibolic. Two of the ectoderm cells in the nine-cell 

 stage are set apart from the rest to form the investing membrane. The 

 embryo soon becomes a syncytium, but separation between the ectoderm 

 and the endoderm usually remains distinct for some time after the cell 

 walls are lost. Sometimes another layer of cells (nuclei and cytoplasm) 

 may be distinguished between the ectoderm and the endoderm. 



The primordium of the gut often retains its identity from the stage 

 when it exists as a single cell after the separation of the two primary 

 micromeres. The primordium of the anterior sucking disk, pharynx, 

 and oesophagus becomes marked out at the anterior end of the embryo. 

 The water- vascular system arises as two lateral intracellular tubes, one 

 on either side of the body. The flame-cells arise in connexion with 

 some of the meristem nuclei, and later acquire their connexion with the 

 lateral trunks. The reproductive organs arise first as a single mass of 

 cells, which later become separated into recognizable primordia of the 

 testes, the ovary, and the accessory parts of the reproductive system. 



The life-cycle of the Malacotylea may be characterized as heterogeny 

 with pedogenesis. 



Parasites from Fishes from Irish Sea.* — Jas. Johnstone has 

 notes on Lebouria idonea Nicoll, from a dragonet, Prosthecobotlirium 

 dujardinii (van Beneden) from Raja macidata and EcJieneibothrium 

 variabile van Beneden, E. dubium van Beneden, and Rhinebothrium 

 minimum (van Beneden) from Rays. 



Fasciolopsis.f — Henry B. Ward discusses Fasciolopsis basJcii Stiles, 

 a Trematode parasitic in the duodenum of man in India, Siam, China, 

 Assam, and Sumatra, and very common in Chinese pigs, and F. rath- 

 houisi Ward, also from the human intestine in China. 



Cysticercoid from a Jerboa-flea. J — Alfons Dampf describes a 

 Cysticercoid from the abdominal cavity of Mesopstjlla eucta sp. n., a flea 

 found on the jerboa, Alactaga jaculus, of Turkestan. No tapeworm is 

 known in the jerboa. The hooks of the Cysticercoid are very like those 

 of Hymmolepis nana. 



Genus Allocreadium.§ — Ivan E. Wallin describes AUocreadium 



lobatum sp. n., a Trematode from the stomach of a fish (Semotilus 

 bullaris), and A. colligatum sp. n., from the intestine of Labrus mixtus. 

 He discusses various other forms, and gives a very useful diagnostic key 

 to the species of HeJicometra, AUocreadium, and Lepocreadium, within 

 the sub-family Allocreadiinse. 



* Lancashire Sea Fisheries Lah., 18th Rep., pp. 16-37 (11 figs.). 



t Trans. Amer. Micr. Soc, xxix. (1909) pp. 1-16 (2 pis.). 



I Centralbl. Bakt. Parasitenk., liv. (1910) pp. 452-4 (2 figs.). 



§ Trans. Amer. Micr. Soc, xxix. (1909) pp. 50-64 (2 pis.). 



