They were the first species to develop mesoderm. That mesoderm tissue develops into organs and muscles as the organism grows. They also have simple nervous systems and sensory organs. While they don't have a respiratory system or circulatory system to speak of, they do have a neat little digestive system. Most species of flatworms have no anus and a cavity with only one opening. While not all species do, many flatworm species use a mouth to eat. The only problem with no anus is that the stuff you don't digest has to go out the mouth when you're done. Other materials that need to be removed from the system can be excreted through specialized cells called flame cells. Flame cells are the first appearance of excretory ducts in organisms. Flame.
1 Some clinics and animal hospitals can charge up to $200-$300 or more, depending on the weight of the dog. 2  The cost of both neutering and spaying vary greatly by geographic region, and even by veterinarian. But lower cost sometimes means an assembly-line approach is used, so the dog might not get as much attention or recovery time. 2  Spay/USA has a referral service for reduced cost spay and neuter clinics. 3  In rare cases, such as with programs that use veterinary students, spaying and neutering can be free.
The cost... The cost for a Neuter certificate is $75 and a Spay certificate is $95. As anyone who has researched spay/neuter surgeries for rabbits knows, a neuter may cost $200+ and a spay can be $400+.