(Gr. diastello, I separate or expand). The expansion of a contractile cavity such as the heart, which follows its contraction or " systole"." Diatomaceae (Gr. diatemno, I sever). An order of minute plants, which are provided with siliceous envelopes.


(Gr. dis, twice; bragchia, gill). The order of Cephalopoda (comprising the Cuttle-fishes, etc.) in which only two gills are present.


(Gr. dis, twice; kuon, dog; odous, tooth). An extinct order of Reptiles.


(Gr. dis, twice; delphus, womb). The subdivision of Mammals comprising the Marsupials.


(Lat. digitus, a finger). A finger or toe.


(Lat. digitus; gradior, I walk). A subdivision of the Carnivora.


Walking upon the tips of the toes, and not upon the soles of the feet.


(Gr. dis ; meros, part; soma, body). An order of Arachnida, comprising the true Spiders, so called from the marked division of the body into two regions, the cephalothorax and abdomen. The name Araneida is often employed for the order.


(Gr. dis, twice ; muon, muscle). Applied to those bivalve Molluscs (Lamellibranchiata) in which the shell is closed by two adductor muscles.


(Gr. dis, twice; oikos, house). Having the sexes distinct; applied to species which consist of male and female individuals.

Diphy dont

(Gr. dis, twice; phuo, I generate; odous, tooth). Applied to those Mammals which have two sets of teeth.


Detached reproductive portions of adult Calycophoridae, an order of oceanic Hydrozoa.


(Gr. dis, twice; pnoe, breath). The order of fishes represented by the Lepidosiren.


(Gr. dis, twice ; pteron, wing). An order of insects characterised by the possession of two wings.


(Gr. diskos, a quoit; eidos, form). Shaped like a round plate or quoit.


(Gr. diskos, a quoit; phero, I carry). This term is applied to the Medusae, or Jelly-fishes, from their form; and is sometimes used to designate the order of the Leeches (Hirudinea) from the suctorial discs which these animals possess.


(Lat. dissepio, I partition off). Partitions. Used in a restricted sense to designate certain imperfect transverse partitions, which grow from the septa of many corals.


Applied to the quickly growing end of the hydrosoma of a Hydrozoon; the opposite, or "proximal," extremity growing less rapidly, and being the end by which the organism is fixed, when attached at all.


(Lat. dies, day). Applied to animals which are active during the day.


(Lat. diverticulum, a by-road). A lateral tube with a blind extremity springing from the side of another tube.