SCIENCE-GOSS//\ 



18: 



having become two. In this stage the little 

 creature searches for a suitable spol for a per- 

 manent residence. The two antennae which pro- 

 ject from the shell pour out a glul inous gum which 

 hardens in the water and fixes them. Another 

 moult takes place, the bivalve shell is thrown 

 off, the carapace is composed of several pieces, 

 whilst the legs are modified into cirri and made to 

 i their grasping movement. Fig. •'> shows 

 ature barnacle with cirri. Nothing can be 

 more effective or beautiful than the manner in 

 which the cirrus obtains its prey. The cirri are 

 alternately thrown out and retracted with greal 

 rapidity, and when fully expanded the plumose 



eve. • 



Fie. 2. Cypris stage of Balauus. Ventral view. 



and flexible sterns form an exquisitely beauti- 

 ful apparatus, admirably adapted to entangle 

 any nutritious atoms or minute living creatures that 

 may happen to be present in the circumscribed 

 space over which this singular casting-net is 

 thrown, and drag them clown to the vicinity of 

 the mouth. This action may be easily seen if a 

 small portion of rock be chipped off. having 

 barnacles on it. and placed in a glass with sea- 

 water. A hand-glass will show the beautiful little 

 hand with twenty-four long fingers, the net with 

 which this fisher takes his prey, busily at work. 

 Care must be taken that there are living barnacles 



ttalk 

 oj> — 

 attacAjrrjeQt 



*b« 



Fig. 3. Mature Balanus and cirri. 



on the piece of rock, as many are but empty shells. 

 An interesting slide is Obelia geniculate, (fig. -1). 

 It has double and alternate generations. The 

 polyp bears urn-like reproductive capsules which 

 discharge large numbers of medusiform zooids. 

 Like miniature balloons they float suspended in 

 the water for a while, and then suddenly start into 

 motion with a series of vigorous jerks. They may 

 be considered as swimming polypites with the 

 arms united by a contractile web. They mature 

 and disperse the generative elements, and. having 

 thus fulfilled their function, perish. The ova, 



alter fertilisation, become ciliated embryos, and 

 when affixed rapidly grow into the plant-like 

 see. Sertularia pumila— -another 

 hydroid zoophyte is a very common s] 

 though it makes a beautiful microscopic object. 



every broad-leaved seaweed I;.-'- 2 

 lesser numbers of this zoophyti \ on it. 



QO"jotl\tCO . 



/ t mcduMcf bud 



Fig. 4. Oh a, portion of frond. 



Coryne vaginata (fig. 5) is one of the Athecata — 

 that is. without any theca or calycle. The capitate 

 tentacles bear on the summit a globular head con- 

 sisting of a collection of thread cells, a vigorous 

 battery of offensive weapons. They occur in 

 astonishing profusion, and consist of minul 



Capsules 



ova. ^&2p?j? 



thread; 



"TerjTaeles. 



Fie. 5. ' 



embedded in the flesh, filled with thud, which < - 



tain a long delicate thread capable of being pro- 

 jected with considerable rapidity. Corydendrum 

 parasiticus is a similar creature to the last, but the 

 tentacle- are not capitate. There is something 

 singular about the stems that support the poly- 

 pites; they look as if they acted as capsule- and 

 held ova. ~ This is a foreign species, and I cannot 

 find any description of it. I believe Mr. Sine! told 

 me it came from the Mediterranean. Pennaria 

 rarolina is also a foreign species. Some of the 

 polypites bear gonophores, the budsin which the 

 reproductive elements are formed. 

 (Ti> he continued.) 



