IJfFUSOEIAL ANIMALCULES. 85 



Again it happens in some species, that the egg shell is dispensed 

 with, the embryo being completely developed, so to be able to imme- 

 diately commence an independent existence on its escape from its 

 parent — in other words, such forms are viviparous : examples ai'e 

 met with in Philodina, Rotifer, &c. 



Mr. Gosse writes, of the Asplanchna, that, " the ovum produces 

 the li\T.ng young in the ovisac, which, when matiu'ed, occupies the 

 whole lower part of the parent .... At length it escapes through 

 the o\'iduct and vaginal aperture, and immediately swims freely 

 away." 



"The egg of the Hydatina,'" says Dr. Carpenter, "is extruded 

 fi'om the cloaca within a few hours after the first rudiment of it is 

 visible ; and within twelve hours more the shell bursts, and the 

 young animal comes forth .... In general, it would seem that, 

 whether the rupture of the egg-membrane takes place before or after 

 the egg has left the body, the germinal mass within it, is developed 

 at once into the form of the young animal, which represents that 

 of its parent; no preliminary metamorphosis being gone through, 

 nor any parts developed which are not to be permanent." (Principles 

 of Physiology, p. 362.) 



The first male discovered, was that of Asplanchna Brightwellii, 

 then a supposed species of Notommata, and is thus described by 

 Mr. Brightwell. (Ann. JS'at. Hist. 1848, p. 155.) It is " about half 

 the size of the female, and differs from it in form, being much 

 shorter and of a rude triangular shape. It is more difficult to detect 

 than the female, being exceedingly transparent, and, from the empti- 

 ness of the body, appearing little more than a transparent ciliated 

 bubble. It is very active, and occasionally puifs out the sides of its 

 body, so as entirely to alter its form, and remains thus distended 

 some time." There was no indication of any digestive apparatus, 

 or of matters in course of digestion. 



" At the bottom of the body on one side, is a conspicuous round 

 sperm vessel or testis, in which, under a high power, spermatozoa, 

 in active vibratile motion, may be seen ; and, at its external side a 

 duct, closed by distinct lateral muscles. Connected with the testis, 

 is a well defined intromittent organ, and a conspicuous passage or 

 opening for its extension from the body of the animal. In the 



